If they can make underwater cameras, they should be able to do the same for cell phones, computers, etc. so we won't have to worry about getting them wet, amirite?

They can, they just don't so that if your phone does get wet, you have to spend more money to buy another one.

At first I read "underwear" and i was really confused...

My friend has a waterproof phone (we put it in a bucket of water at church to test it)