I can see what you mean, but it's canon that youkai are naturally asocial and that ones who HAVE formed societies like the Tengu and the Kappa are simply living a travesty of actual human culture.
Huh? You seem to be confusing "having a large, complex society" and "looking for an emotional/friendly connection with another person" - just look at virtually every single character to date. Yes, true: they don't live in "youkai cities" or anything like that (save for tengu and kappa), but that has absolutely nothing to do with "reproductive drive" (your words) or "need for companionship/emotional connection" (my words)...
On the other hand, it's canon that just about every character bar a few small exceptions end up establishing a handful of close friendships with one-another here and there. Even with humans (who
do stand out from the crowd, but
humans nonetheless), like Reimu, Marisa, and Sakuya, and other non-youkai species. Ex, Satori and her pets, Kyouko and Mystia, Suika and Yukari, Keine and Mokou, Rin and Utusho, several characters form larger closely-knit groups (the myouren temple, the SDM group, the eientei group (technically aliens...... Ill concede that much), the four devas of the mountain......) the list goes on and on.....
There's more than enough proof, in canon, that youkai actively seek out relationships. While they're probably not as sociable as humans are, and while there are a handful of exceptions, they're clearly not the asocial beings you seem to be making them out to be, much less "in canon"......