Bettas are not easily bred. They have complications like killing a mate who doesn't feel like spawning or is incompatible with the mate you have selected. Sometimes it takes several bettas to find a compatible match. Most breeders recommend at least two pairs of the same type to mix and match. Many fish will simply refuse to breed if they don't feel like it, at least they won't kill each other.
Then once you are successful, you need to house multiple males in individual containers. This is time consuming to change all these containers, which needs to be cleaned frequently.
IF you do you not buy expensive breeders from private breeders, most people will not buy your common petshop bred bettas and you will lose money breeding these bettas because you won't be able to place them.
Nothing wrong IHO with a beginner breeding these common petshop bettas, just that it won't be profitable.
Then there's the factor of receiving defective/ shipping damaged bettas who not only don't spawn, but are also disease prone and or handicapped and require much TLC to stay alive. There is no lemon law for fish so you are on your own. This will make things less profitable when you factor in replacing losses and shipping expenses.
I'm not sure where they fall in the grand scheme of things, just know they are not easy to breed.