More than half of my work is time and materials work (as opposed to a fix bid project), and so it's directly billed to the client. My putting in hours is directly proportional to how much the company makes.

I don't like it either, and I feel like I could contribute a lot more effectively on the fixed price items if I wasn't constantly scrounging up T&M work, maybe I'd even have time to think up decent solutions instead of justifying why I have to spend another 2 hours on issue #blah, but it's an example of why required hours exist.