Why are your big cat cages so small? Why is there no foliage in the Zebra pen?

I live in San Diego were the wild animal park is I feel the big cats have more than enough room .Maybee not the San Diego zoo though the animals are depressed looking anyways in the future that's probably going to be the only place you are able to see these animals .

The cats do seem sad l guess with any captive wild animals