It's also about 2 times bigger than a lot of SNES and Mega Drive games. Or about 4 times bigger than Super Mario World (512KB).
As for why it's getting so insane, probably either:
1. Frameworks, since most people don't remove the code they're not using. For Bootstrap or Foundation, that can be a lot of extra code.
2. Content Management Systems, since stuff like WordPress, Drupal, Joomla, any forum or social network script, tend to add a lot of extra code (more so if you've added plugins).
As for why it's getting so insane, probably either:
1. Frameworks, since most people don't remove the code they're not using. For Bootstrap or Foundation, that can be a lot of extra code.
2. Content Management Systems, since stuff like WordPress, Drupal, Joomla, any forum or social network script, tend to add a lot of extra code (more so if you've added plugins).
3. The aforementioned tracking codes, ads, etc.