It greatly depends on the breeder's intentions. I think halfbreeds recognized by registrations of either parent are generally done to make a better ____ horse. My filly is an Andi/TB, and she is registered with the ILAHA as half-Andalusian. The fact that she still has to conform to the regulations in the registry and the registration does not prohibit but condones it makes me feel that it's a good thing. I think she will make a splendid sporthorse, having obtained the best traits from both breeds.
What I have a problem with is people with unregistered horses breeding just to breed, then having a baby they don't particularly want. There is a huge surplus of horses in the US and it's not beneficial for the economy or the horse to just keep breeding with no purpose. Horse rescues are overflowing with unwanted horses of every age, breed, color waiting for homes, so it doesn't make sense to me for someone to breed a horse JUST to have a baby.