Actually, while you may call it rescuing, you just added to the problem yourself. It is impossible to rescue them all - the more that get rescued the more get restocked. Our betta was bought in Walmart, but I wasn't rescuing him, I selfishly bought him. I won't buy any other fish from Walmart any more - over the last few years the condition of the tanks in my local Walmart got worse and worse. Now it is almost impossible to find a tank in Walmart that does not have one or more dead fish in them. The one positive thing about the cups the bettas are sold in is that they at least don't have to live in a tank full of dead fish (that would be the other tanks). After I had him temporary in a 2.5 gallon tank for a few weeks (kept looking healthy) he is now rehomed to the big tank and his permanent home. If he stays only in his territory of the tank, then he claimed the whole 180 gallon as his territory. The only places he won't go is the sleeping/hiding areas of the other fish. And no matter where he sleeps the other fish leave him alone - there is multiple spots he likes, his favorite is on top of a powerhead close to the surface.
That is not entirely true. Bettas do make great community fish as they are so very peaceful. They also naturally have the smarts to stay out of trouble and the means to defend their territory. You don't really need a whole tank for one fish, even the 5 gallon tank can happily house a male betta and other friendly fish. Male bettas are not the only fish that should not have company of their own kind, or require special arrangements if attempting to keep more than one in the same tank.
They will only stop breeding so many if everybody stops buying them, IMHO. If they stopped selling all the fish (not just bettas) that mostly get bought and stuck in inadequate environments, then there would be a lot less fish for sale. Without the bigbox stores selling fish, there would be a lot less people interested in keeping them.