But this is not so.
Saint Basil the Great in the 4th century, Saint Alphonsus Maria de Liguori in the 18th, and Saint Francis de Sales in the 17th, all preached on the importance of living the Gospel no matter your state in life. So did Saint Francis of Assisi, in the 13th century.
Although Saint Francis is well-known for founding the religious institutes of the Friars Minor and the Poor Clares, he also founded a Third Order for lay persons.
From The Life and Legends of Saint Francis of Assisi by Father Candide Chalippe:
One day St. Francis having gone from Florence to Gagiano, near Poggibonzi, in Tuscany, met a shop-keeper of his acquaintance, whose name was Lucchesio, who had been very avaricious, and an enthusiastic partisan of the faction of the Guelphs, but who, having been converted a few months before, now lived a very Christian-like life, gave away great sums in alms, attended the sick in hospitals, received strangers hospitably into his house, and endeavored to instil similar sentiments into Bonadonna, his wife. They had already asked Francis to put them in a way of sanctifying their lives, which should be suitable to their position; and the holy man had given them this answer: "I have been thinking of late of instituting a Third Order, in which married persons might serve God perfectly; and I think you could not do better than to enter it." After having given the subject serious consideration, Lucchesio and his wife entreated him to admit them into this new Order. He made them assume a modest and simple dress, of a grey color, also a cord with several knots in it for a girdle, and he prescribed verbally certain pious exercises, which they were to follow until such time as he should have composed the rule.
This was the beginning of the Third Order of St. Francis, which many persons in the environs of Poggibonzi embraced, and which was soon established in Florence by the congregation of men and women of which we have just spoken. The following year, at latest, the Founder composed a rule for this Order, which he called the Order of the Brethren of Penance, in which the sisters were comprised, which was also called the Third Order, or the Order of Tertiaries, as relative to the two older Orders: the Order of Friars Minors, which is the first, and that of the Poor Clares, which is the second. This rule was subsequently confirmed by Pope Nicholas IV, and Leo XIII, with some changes, which they considered advisable as well in regard to the times as to the Order itself.
The holy Patriarch manifests therein not only the zeal which animated him in all that concerned the purity of the faith, but also the prudence which guided all his actions. He requires that all those who apply for admission into the Order shall be carefully examined in the Catholic faith, and their submission to the authority of the Church, and he directs that they shall only be received after having made profession of all the orthodox truths; and that great care shall be taken not to admit any heretic, nor any one suspected of heresy; and should any such be detected after having been admitted, he insists on their being immediately informed against. He, likewise, directs that their previous conduct may be inquired into, to ascertain whether any notorious crimes are imputed to them, or whether their morals are irreproachable, and he desires that they be warned to restore what they have which belongs to any other person; he also forbids receiving any married female into the Order without the consent of her husband.
The profession consists in a promise to keep all God's commandments, and to perform such penances as the visitor shall enjoin for faults committed in breach of the practices required by the rule. The habit is similar to what was given to Lucchesio and his wife; but so, that this may be dispensed with, according to the state of life of the persons, and the customs of the country in which they may be. The spiritual exercises laid down in the rule, have nothing in them which can interfere with the different stations of persons living in the world. Days of fasting and abstinence are prescribed, but modified prudently for the infirm, for pregnant women, for travellers, and for laboring people; and it is clearly explained that these observances are not obligatory under pain of sin, and that they only bind the transgressor to perform the penance imposed on him, unless the transgression has at the same time contravened any law of God, or commandment of the Church.
St. Francis, moreover, strenuously recommends to the brethren and sisters, to avoid all words tending to swearing or imprecation, the theatre, dancing, and all profane meetings; to undertake no law-suits, and to live in fraternal union; to take great care of the sick of the Order, to bury the dead, and to pray for them.
He adds to this, an article which is deserving of peculiar notice; it is, that all persons who enter the Order and have property over which they have the disposal, shall make their wills within a few months after their profession, lest they should die intestate. We see that his intention was to make them think on death, and to have their minds free for meditating on the important affair of their salvation, and to prevent those dissentions which frequently occur after the death of such as have not regulated their temporal affairs, before being called away. Wills which are made during a last illness are frequently exposed to deceit and fraud. They are never better made than when executed while the testator is in good health, in possession of all his faculties.
By the institution of the Third Order, Francis proposes to himself to reanimate the fervor of the faithful, to induce all the world, those in orders, laics [the laity], married persons of either sex, and such as were living in a state of celibacy, to a stricter observance of God's commandments, to live a more Christian and Catholic life, and to add the practice of virtues to the duties of civil life. His views met with astonishing success; the Order was established, and spread with the greatest rapidity through all conditions of life. Cardinals, bishops, emperors, empresses, kings, queens, considered themselves honored in being admitted into it, and it has given to the Church an infinite number of saints and blessed of either sex, who are publicly revered with her sanction. Wading says, that in his day, (that is in 1623,) there were at the court of Madrid more than sixty lords who belonged to the Third Order; and Cardinal Trejo, who had joined it, wrote to him in these terms on the subject of the works of St. Francis, which that author was about to give to the public with learned notes.