Its cause there are wayyyy too many VT's out there, and from what I've noticed not as many people are like OMG VT!!! and are more OMG HM or HMPK!! But as far as guppies go, go for it :D they are super easy to breed and care for.
Nope, my males got the girls preggers. But not many babies lived sadly.
If You're thinking about breeding bettas, first think about how many there are out there that need homes. :/ however if you have a good breeding pair of non VT's and have read up on it, then go for it. Just know that keeping the fry alive takes a lot of work and that in the end, you won't make much off of them. Store credit sounds nice though :D I'd love store credit at one of my local pet shops that sells the foods and items I use most. AND they have every few animals for sale, since they buy from breeders, >> thats where I got boo and my super old fish pixie.