Why does someone have to wait for registration? I thought that you could just purchase a steem account from one of the witnesses automatic registration site.

You pay steem, you get the keys sent to you. Yes this causes a delay, but what other coin with limited available real estate (easy to remember steem account names) allows spamming of the best and most easy to remember account names. Pascal Coin makes you purchase their accounts. This is necessary to eliminate spam that could bloat the chain. All chains with customizable addresses have this issue. Bitcoin does not have this issue because the account names are mostly gibberish like: fusihfir7834fh43h87h78g78g6T7G76FG6ihyg