Another possible reason – was this her first litter ? Most wild animals have a difficult time with first litters and may abandon them because the mothers themselves are immature.

“In addition to starvation, cubs also face many other dangers, such as predation by jackals, hyenas, leopards, martial eagles and snakes. Even buffaloes, should they catch the scent of lion cubs, often stampede towards the thicket or den where they are being kept, doing their best to trample the cubs to death whilst warding off the lioness. Furthermore, when one or more new males oust the previous male(s) associated with a pride, the conqueror(s) often kill any existing young cubs, perhaps because females do not become fertile and receptive until their cubs mature or die. All in all, as many as 80 percent of the cubs will die before the age of two.”

Unfortunately, if these little guys were born in the wild they wouldn’t have very good chances of survival even if their mom didn’t turn them away (and it would be zero if she did).

Given how many animals are close to extinction and how valuable being able to see them up close can be to children (the future decision makers) and adults, I think zoos serve a valuable environmental preservation purpose and they can be non-terrible options for animals (certainly better options than being left in the wild to be poached and possibly exterminated).

I can sympathize with your point of view, but until such time as people can actually leave animals alone and not destroy their natural habitats I think zoos will continue to be an important tool and for helping people appreciate why we need to slow down our abuse of the environment. Furthermore, leaving animals in the wild would mean that those 3 little guys almost certainly would have perished by now.