You’re earlier point about contraception has more than bit of truth to it - Catholic families having fewer children results in a diminished pool of “talent” from which propositive priests can be drawn.
Yes, that, and also what I think is the very real idea that marriage, with one, two, or possibly three children, both spouses working in satisfying careers, living “the good life” (in the world’s eyes), nice big home, plenty of money in the bank, having those children only when you want them and not a moment sooner, in the quantities desired, is a more attractive proposition, than surrendering to what might be either unbridled fertility — NFP doesn’t always work, and “back in the day”, the rhythm method was
horribly unreliable — or prolonged periods of unchosen abstinence.
I have noticed that religious, and to a lesser extent priests, tend to be
very long-lived, and not to be crude, but they generally age well, you can tell just by looking at them, that they have not had materially difficult lives — they have satisfying “careers” (so to speak), they get an education (sometimes a very good one, bachelor’s and master’s), they don’t have to worry about the needs of a family, they can’t be fired, their basic temporal needs are provided for life.
Sounds pretty good to me!
And from a spiritual standpoint, it can’t be ignored that religious life is intended to make it easier to save one’s soul. By contrast, it is
harder for priests to save their souls, because they are responsible for leading their flocks to heaven, and have to deal more directly with the secular world, whereas many religious “live in a bubble” and only have to worry about their own salvation.