To be fair, I'm pretty sure this is a limitation that the carriers insisted on, at least in the U.S. There is no advantage to limiting download size for Apple. As you demonstrated, it just annoys their customers.
On the other hand, think of all the people who have complained about the forever-to-download app that is stuck on their iPad. Imagine how many more complaints there would be if they were using 3G for the really big ones.
Could be just a case of guessing which group would be smaller, and complain less. The tech is still far to limited to meet everyones expectations and/or needs.