On a good platform there is one default profile and there are profiles with optimized settings made for this to keep the amount of people who need to fine tune their ideal settings to a minimum. The type of screen also matters in that regard (the greasy screens are a bit harder to read from but they work better in the sun; again, sacrifices).

They exist, but they are hidden from the masses because they don't care about this. If they are not hidden to the masses and the masses are not guided you get a chaotic mess of confusement, or people with too much time figuring out what is best for them. So instead of having an ICQ Messenger, an AIM Messenger, an MSN Messenger, IRC chat, Yahoo Chat you have by default Pidgin and it does all of that reasonably well. If I install Ubuntu Desktop I get Pidgin. Maybe I'd like a dialog when I install Windows, to ask me if I want Mozilla Firefox, Opera or Microsoft Internet Explorer. I wouldn't pick the latter then, and at the very least I want the choice to have applications use something else than MSIE or Trident to render their stuff. And instead of having 100 choices you need to make clear to the customer why your product is better. For example because it contains less fat, or because it has some official label, or some random buzzword.