Satoshi wanted BTC to be like gold: initially easy to create but then increasingly more difficult. I don't think he put a ton of thought into it. This algorithm will work fine, though.
It's kind of odd, though, that he would just arbitrarily pick a tapering-off point, after all the work he put into the rest of the system, isn't it? It's almost like he didn't care about the economics of it, and just wanted to test the soundness of the algorithm for handling transactions.