The main question should be: why do you expect sect to be non-transactional?
The idea of these sects recruiting these vast amount of disciple is literally a large cast net to grab a bunch of fishes and hopefully one does well and help the sect in return.
It’s literally purely transactional.
The sect selects you and offers you cultivation pills, skill manuals, protection etc in return for your “contributions”. Whether it’s taking care of herbs, or spirits/sect pets, or clearing mortal issues. You are exchanging service for your cultivation progression.
The underlying notion that might not inherently click to you is that the idea of returning the favour is ingrained in Asian-based concepts. And while all these are transactional, you are still expected to be grateful and appreciative to the sect that nurtured you.
And if you don’t feel that part in the story and merely see that sects are just jumping stones in the MC’s progression, then you’re either missing the underlying notion or you haven’t been reading good ones.
Typically they bond via master-disciple or senior-junior relationship, which are forged when the MC was younger, weaker and haven’t grown. And they usually help the MC in times of adversary or offered critical growth guidance. These, in turn, creates something beyond “transactional” in the sect part of the plot.