Facebook Apps and Profiles

So I’m not really into the Face­book thing, but occa­sion­ally I hop on and see what people are up to. I’ve noticed a few of my friends have some inter­est­ing look­ing apps on their pro­file pages, and figured I might try some of them out. Except for, every single one I’ve looked at so far insists on get­ting access to my com­plete pro­file. Why? I can­’t ima­gine why an applic­a­tion that pops up pic­tures of cute cats needs to know where I live, for example, or why any applic­a­tion needs my birth­d­ate. It should be easy enough to assign some ran­dom iden­ti­fi­er to my account for most needs that these apps have, such as count­ing how many sub­scribers they have. Why do they want more?