I think it is a matter of personality. In my (long) life I have come across 4-5 incidents of animals, especially dogs, being regarded as disposable or as toys to be discarded. Two of these involve families who were basically stupid, never took exercise themselves, and were constantly baffled by the fluffy new pup going stir-crazy, eating the furntiure and having to be put down. The other two werre intelligent professional people - who probably regarded the people around them as equally disposable. Both of these independently and at different times had an animal killed as it was cheaper than kennels when going away on holiday. They would probably have had their workforce put down if the law allowed it. Another professional person sold their dog as it was not fashionable enough.
But these nasties have thankfully been in the minority.