There aren’t really any alternatives to Comic Sans or Papyrus on Windows. Everything else looks awful when printed (Verdana) or is, if somewhat more – ehem – professional than Comic Sans, not exactly very emotional (Times New Roman).
They always had Arial. But that is even more formal, as we're used to sans-serif fonts in signage. If you want to inform someone of the fact that there are cookies in the kitchen, you don't want to present it in the visual equivalent of a German border guard.
But never mind what's the original reason, now people are used to these bad fonts. A corner cafe using Papyrus, birthday invitations using Comic Sans… My point is that you could harness that history if you want to advertise your business on the web. Will it be good typography? Nope. Will it sell more than a golden ratio Bodoni layout? Possibly.
