The Curse of Confirmation Mails

I guess I am not the only one who has to wait for signup confirmation mails. I am sitting here again, waiting (im)patiently for a simple email to finally show up in my inbox. Why in Gods name does every site require email confirmation [i]before[/i] I can actually use it? Why not let me do whatever I was planning to do, like filling out my profile, posting threads, whatever, and let me confirm it [i]afterwards[/i] to make it show up?