I don't agree to your statement that "people who pay for it haven't yet found an easy way to make sure it isn't abused for spam accounts", I am sure people pay and create many accounts to gain popularity in the early stage.
The other day a guy was telling me in general chat that most of the people even do not read any post, but some posts end up with high no of upvotes, because they have bought power and use that to make it popular. And I don't see any reason why they can't do it, its a kind of investment they are doing.
What @troglodactyl said is correct: steemit has to pay the blockchain for the accounts that it gives away for free. And it's difficult for them to be sure they don't hand out a lot of free accounts to the same person, they need to verify their identity to avoid that.
So the solution would be hire a person to only do that(verify identities)... or even contract a verify system that can do that automatically such as netVerify for instance. Dont you think that?
And why ned or dan didnt take into consideration that this WILL happen? Another solution might be a way to charge us i dont know like the 1% of our curation or post rewards to help the account creation cost. Personally i think that the new users are the gold rush here and everywhere! Or Coca-Cola is what it is because it have only 300.000 users around the world? I dont think so. It's one of the reasons i have not been writing post yet. Because my followers in the others social platforms wont wait one month or more to get their Accounts approved! And as you may know, take the attention of people on something isn't easy. Once you have their attention, you have to do/give/provide the best, and the best is not have to wait such a long time for sign up.
Take into consideration my 1% fee or something like that for a "pool to pay the fees involucrated into account creation"