IMDB Treating Chimps Like Man

While looking up something about Mathew Broderick on IMDB (it turns out the "trivia" section doesn't say how he keeps his boyish good looks), I came across the listing for 1987's Project X, starring the young actor as an Air Force cadet in charge of watching some chimpanzees being used in a project.
This alone didn't bother me that much--movies like Ed and MVP: Most Valuable Primate have numbed me to the terrible genre that IMDB has dubbed "simian fiction"--but what did fill me with unbridled rage was noticing that not one, but ten chimps are given higher billing than Matthew Broderick.
Don't get me wrong; I couldn't care less about where his name appears in the credits. The issue is this: why are we treating screen monkeys like actors? (Moreover: people.)
Jesus, they're trained animals. It's not like they're up there actually emoting. Having some peanut butter smeared on your gums to make it looks like you're talking, or jumping up and down as your trainer waves a baton, should not qualify you for your own IMDB listing.
What is the point? Am I supposed to know these guys, have favorites?
"Who is that playing Goofy? He's really good. Wait, that's Okko? I love Okko! I thought I recognized him. He's my favorite screen chimp."
Are there legitimate reasons for this to exist, outside of angering me? Who is your favorite screen chimp?
