The right suit is cool, but keep in mind the Zero Suit is meant to be worn inside the Power Armor. So all that extra layer is kinda hard to get into the bulky Power Armor. The Zero Suit is kinda like a second skin, y'know?

I think that the point of the Zero Suit is wearing something flexible and skin tight so as to avoid having a loose suit that feels uncomfortable, but most probably, because it contains sensors to control her battle suit with her mind (because future science, that’s why)