As if humans aren't animals? We developed because we were able to apply experience rather than instinct. Our experiences made us teach things, things we applied in similar situations that helped us stay alive. Now look what we have in opposition to 'regular' animals, there's human rights, laws that forbid us to kill others, and an economic system that rewards us whenever we are performing well (not mentioning exceptions here). Cats won't learn not to kill because people don't want them to, believe it or not, but from an objective view, such cat owners are sadistic beings. The Pavlov method applies to every animal so far, why would a cat owner not apply it to his or her cat in order to tame it? Also, cats themselves should be taught some decent values as well. They see the hunting of smaller creatures as playtime. This is motivated by most people for no apparent reason. Whenever you see a dog shred a cat to pieces, people either try to stop the dog or punish it for what it has done. Cats however, are rewarded for their killings.
Clearly anybody with some sense does not approve of cats in their current form.
It is like that because apparenly we don't care about smaller animals like bugs and mices, who are annoying for us, people. WHy would I be angry IF a cat killed a mouse or a bug/cockroach in my house or flat? I don't want these creatures to live at my place therefore I would kill them myself if I had the chance. Fortunately, My cat did it.
And only the cats who live at home are doing the things you mentioned, those who who don't have owners and live in a city don't do it, I mean play with the smaller things.