I don't know why they don't have that for comments on profiles.
They do, but it isn't very noticeable. You'll see it when you're trying to post a comment on someone's profile but instead of your comment appearing, the most recent comment appears a second time. This means that you haven't waited 30 seconds since your last comment and therefore your comment will not post.
Yeah, that 30 second rules doesn't really work, does it? It seems that even people who think spam is annoying spams.
There is a 30 second wait on posting and commenting (profile and game), and while it might be annoying, it can be used to think of what you are going to say in the thread, look through the post to make sure you didn't make mistakes, and other wondrous stuff.
