Well, since I was breeding a lot of plecos, I was feeding a lot of babies. They need a lot of food and no matter how well one cleans such tanks, there is always some excess food the snails can get. That gave me the pest snails. This leaves one with two options, either kill the snails or use them as food for the assassins once they have done the job for which one acquired them.
I would say that the only live food I do is feeding the pest snails to the the assassins. I see it much like angel breeders who feed their culls to something. Or how about folks who keep puffers and feed them pest snails?
Finally. almost anybody with a planted tank has some familiarity with snails they never wanted? It isn't as bad as free duckweed, but it can be close. And then there is the cash selling assassins brings. It may not be a lot but it does help pay for a bit of one's fish hobby.
But when it comes to assassins and other inverts breeding, it isn't only food that matters, water parameters also count.