a) Licensing, bundling firefox with such components would create havoc in the land of GNU and other groups / persons that doesn't want to download applications with bundled software.
b) There is already a wizard for installing those components, so you can't say that they haven't tried to make it as smooth as possible. In my opinion, it is better than bundling it as it gives the user the option to say yes or no. (Yes, some of the more core components have to be downloaded manually. I'm sure a user can live with that, even though it might be hard.)
c) We're not
Mozilla. Suggestions don't go to us.