The category exists because a genuine alternative to monastic life had to be invented, and it was invented on purpose. Monks were defined by stability: a vow to remain in one house, supported by land and endowment, withdrawn from the world it prayed for. In the early thirteenth century, Francis of Assisi and Dominic of Guzman each founded a different kind of community, the friars, whose members moved between towns, owned no property individually or, in the earliest Franciscan practice, collectively, and supported themselves by begging rather than by rents. The friars were built for cities rather than for the countryside estates monasteries typically held, since preaching and hearing confessions required proximity to people rather than distance from them.
Rome recognized how great a jurisdictional break this was: mendicant orders were placed under papal authority directly rather than under the local bishop, freeing friars to preach and hear confession across diocesan boundaries that would otherwise have required a bishop's permission, a privilege that caused real friction with parish clergy for centuries. Later congregations pushed the same logic further still. The Jesuits, founded in 1540, dropped the daily choir office and much of the distinctive habit that even friars kept, becoming clerks regular whose entire form was built around mobility and active ministry rather than any fixed community life at all.