They don't when they make money... Ever seen Blackfish? (2013 documentary film). Mainly focuses on the killer whale Tilikum at Seaworld. Killed 3 people- 2 trainers and a guest. Poor thing had a miserable life. The film is utterly heart breaking:
'Experts diagnose that SeaWorld's infamous killer orca Tilikum had psychotic rages during its 30 years in captivity.'
Once the final trainer had been killed, they finally stopped trainers going in the water with him. He would just lie there motionless for hours in a tiny holding pen, then be dragged out at the finale of a show. Rather than just release him into an outside pen to live out the rest of his retirement, they decided to breed from him. Poor thing finally died in 2017 in captivity. Must have had a dreadful life.
Thank God, they have finally announced that they will stop the breeding programmes and phase out the orca shows.
Honestly, it's a brilliant film- if you can bear the sadness. It is quite unbelievable what a cruel race we are. Yes, we do sometimes show animals mercy but not if we can make a profit out of them.
Still- I agree with your sentiment. We put down our pets because we don't want them to suffer. I agree- it's all messed up.