I think fish farmers have a lot of time on their hands while waiting for the fish to grow up to saleable size.
They could also be staring at their tanks and tanks of ugly-nobody wants fish and try to make something new.
This is following the 'new is more expensive rule' to make some money out of rejects.
For them this is a much faster way than waiting for mother nature to create something and wait for some fish scientist to discover it and figure out it's mating habits...
BTW hybridising and line breeding are different techniques. one is cross species, the other is refining a trait thru selective breeding. [just in case some of you guys forgot what you were arguing about. 
]
So parrot fish and flower horns are on same level which are hybrids where a couple to a cocktail of species are used.
Thanks for the parrot fish parentage info pilikpalak. However i have this to say.
Creating a fish that can't close it's mouth is really dumb, not critisizing the people who like/love this fish but the people who created it and made it available for sale.
Line bred discus are like most guppies and bettas where careful selection of desirable traits are bred.
These still carry the latin name with a sp to it. eg
Symphysodon aquefasciatus sp.
I draw the line where people try to create angelfish/batwing discus and spinal cord disaster discus or balloon rams. that's like make a dog fit a purse...distorting it's shape. instead of built for the kill it's now built for the 'oooh so cute crowd'...
if you want batwing discus, buy bats and discus. if you want balloon rams buy balloons and ram it?
my two sen.
regards stan