Why it is important for "Environmental Enrichment" in zoos?

I hear about zoos putting toys or logs to encourage animals to practice their natural skills, but why is this important? Couldn’t the animals do without these things?

I think they don’t want the animals to get too bored. And, if nothing else, letting them play makes for more interesting creatures.

My understanding is that , even in modern zoos, which have tried to get far away from the older Bare Cages with Bars in favor of more natural environments, there’s still the problem that the environment is pretty small compared to the creatures’ natural ranges, and in that things inside don’t change much. The Environmental Enrichment is supposed to give the animals new experiences and puzzles that occupy their talents and need to explore and keep them from getting bored and lethargic. In the abswence of new challenges and a changing environment, animals seem to get into a state of depression. These “toys” fix that. Seems to work at our zoos.

Horses kept in paddocks instead of will develop many obsessive-compulsive behaviors; cribbing (chewing on the wood of the paddock walls), pacing, walking in endless circles.
Stable vices. Info at bottom of page.
You see the pacing behavior in large cats (tigers etc.)
Imagine yourself locked in an empty room 24/7.

Also, I imagine you want to keep it as close to nature, because then you don’t have to deal with weird unnatural problems. Like a caged animal with all the food they want will probably get overweight, and then you have to deal with that. Or if they don’t use their claws, they may grow out too long and you have to trim them. That kind of thing.

I saw a result of not enough stimulation in the Bronx Zoo in the 70s. They had begun giving the animals things to do, but for a few, it was too late. There was one older polar bear who stood in one spot and kept moving his head back and forth. From what others were saying, he did this all the time. It was clearly some OCD behavior, and for that reason, zoos (who have enough headaches defending themselves these days) are careful to give their animals mental stimulation/play/socialization.

A desirable side effect of such enrichment is that zoo visitors get to see the animals out and active =-- actually “doing something” rather than just sitting or lying around. It’s a win-win situation.

(On a darker note, I have to add that another positive benefit is that it keeps zoo patrons from provoking the animals or inappropriately feeding them – both harmful activities that patrons should not do, but which I’ve witnessed often enough.)

Not to mention that active, involved animals tend to be healthier and live longer. This is better for the animal, obviously, but it’s also better for the zoo: healthier, longer-lived animals cost less both to care for and replace. Win-win as CalMeacham says.

The question could easily be phrased “why not give animals toys/logs/features?” and I doubt there would be any good answers.