Can’t say I’m sad to see it go

Microsoft has announced there will be no more Internet Explorer versions for Macintosh. I do everything I can to avoid using it anyway, so it doesn’t much affect me. However, I would like someone to explain this quote to me:

Sommer said that, with the emergence of Apple’s Safari browser, Microsoft felt that customers were better served by using Apple’s browser, noting that Microsoft does not have the access to the Macintosh operating system that it would need to compete.

Why exactly does MS need access to the OS in order to compete? Mozilla doesn’t, and I think Firebird is better than Safari.