The demand of Sign Ups is high enough i think, the process of approval of each account is what makes the process slower, but i guess it is because of the stability of the blockchain.
As every post, comment, upvote is a transaction itself, duplicate the users could mean duplicate the traffic, and at the end duplicating the transactions.
Steemit is great because you make all those kind of transactions with NO FEES and in A SECOND, that makes Steemit better than any other cryptofunded project around, because it has a Coin 100% usable.
But in order to keep the stability and taking the scalability into account, the Sign Up process should take some time, as it is doing right now. Great for us that are already in making good content!
#keepsteemin my friend!