Sometimes it can be a real hassle to retrieve your iPhone cable to transfer a bunch of new games and apps. Apple has become aware of how many people like to download on the go over the years, increasing the limit of how much data can be transfered bit by bit (heh). For the last year the limit has been 50mb, and while this has been great, the games and apps available are always becoming larger, and more robust. This calls for additional download capacity.
That must be why with their latest iOS update, Apple have increased the over-the-air download limit to 100mb. This will alleviate some of the pressure from those on the go who wish to engage in some new app grabbing.
Of course at home, your phone really should be connected to your wireless internet if you have it. It solves a lot of these problems.