Because the people that do desktop support don't want to support more browsers than the minimum possible. I'd bet a decent proportion of desktop support calls a

Because the people that do desktop support don't want to support more browsers than the minimum possible. I'd bet a decent proportion of desktop support calls are about 'problems with the internet' (read: browser) and starting every one of those call with "are you using IE or Firefox?" would most likely get answered with: "I dunno! I want to use Google!"