Why isn't samus in a mario kart game?

[superchunk]

The Ghost of RubangB said:
I don't buy the weapons defense or ship defense. If Samus got her own weapons, then Mario would be able to shoot fireballs, turn invisible, turn into metal, fly in a raccoon suit, tanuki suit, or a cape, and if Samus gets her ship Mario could get his ship from Super Mario land.

 no see, Mario requires the upgrades and his stuff is temporary. Samus' arm cannon is permanent and requires no upgrades. Plus, she usually loses her stuff in the beginning and THEN requires upgrades.