Blame limitations to wireless air delivery on telcos. They have it at 100MB now limit but before it was 50MB and before that it was 20MB. They telcos prevented files/apps over that size from being transmitted over their wireless networks.
Yep, but Apple really should have increased the limit for updates to match the limit for app sizes. It's pretty ridiculous that you can download as many 99mb app installs and updates as you want, but be denied a 10mb critical security patch over 3g.