Hi Smuscles,
Yes … I think a mattress protector is important to protect the mattress from body fluids, stains, and accidents. There are several types and each has it’s own pros and cons and tradeoffs involved which you can read about in post #89 here.
the thin membrane type such as the Luna are a popular choice because they are waterproof and they are also thin and stretchy so for most people they have little effect on the feel of the mattress. The tradeoff is that they are less breathable and ventilating than the other two types and for some people they can increase the sleeping temperature of the mattress.
Phoenix