We don't just do it so that the feral cat population can continue to multiply. And we won't go over to a stranger's house and feed the stray cats who are annoying - if you feed them, they stay.
One reason that we feed cats is to get them comfortable enough that we can trap them and then move them to a better location. Hopefully, that means getting them adopted as pets.
We also feed the kitties in our Trap/Neuter/Release program. Here, the idea is to let the feral cat population slowly and naturally decline. Since no new kittens are being born to the neutered ferals, as nature takes its toll, the colony gets smaller and smaller. The local colony that we feed has dropped from a high of eight to only two cats. It took a while, but it was cruelty-free.