Because it works. I have never wanted to do anything on my iPhone that I can't and as a developer I've only had one rejection that annoyed me and in hindsight I understand the rejection. I've also used Android devices a lot (I own two, and develop for the platform) and I hate it. Really hate it. Waiting for OS updates, lots of crashing, things in different places depending on the OEM. Not to mention how slow some devices are. The S3 Mini is horrible to use, I don't see how anyone could feel comfortable putting it to market.

In short, the crap either doesn't effect most people, or creates a better experience. The only people who seem to really complain about it don't use the platform anyway.