Cryptocurrency exchange needs more info than any bank or brokerage firm? I wanted to quickly sign up for a cryptocurrency exchange today to act on some info I found out about a low-cost coin (hahahah, quickly. how naïve).  In signing up for the account, I got to a step asking me for my SSN, which is pretty normal. But then it asked for high resolution photos of a picture ID AND a proof of residency document??  

I have MULTIPLE online bank accounts and brokerage accounts, with tens of thousand of dollars being held and traded in various forms, and I've never had to provide such information. Why the heck is the supposedly "anonymous decentralized currency of the future" requiring me to send in my firstborn and the results of my latest colonoscopy??
The requirements vary by exchange and are mostly as dictated by the regulating government. Bitcoin itself is decentralised, however, exchanges and businesses operate within government jurisdiction and must comply with any regulatory requirements. The requirements are usually country specific but mostly revolve around anti-money laundering requirements and whatever their standard requirements for investors are.