see? all of them have their upsides!

Chrome is fast
Firefox is balances, and overall effective
opera is just as effective as Firefox
mac os X is shiny
Internet explorer is stupid, insecure, and slow. OH WAIT, I guess it is... built into the operating system? Yeah, so people don't have to download it themselves. It is easy for people who aren't tech savvy enough to know that it is a horrible browser. Plus it is great for downloading firefox and then promptly destroying.