Why wikipedia is brilliant:

Advantages and disadvantages of jumpsuits

Advantages:

You never have to worry about how to combine your clothes, since the jumpsuit is the one piece of clothing you need.

Since jumpsuits have an unbroken line from the neck to the foot of the body, it gives a slimming impression which is flattering for most people's bodies.

It is possible to get in or out of a jumpsuit very quickly. Jumpsuits are usually comfortable.

If you fall backwards in the snow while you are wearing a ski jumpsuit, you won't get snow down the back of your pants.

Disadvantages:

As the jumpsuit has to fit the whole body, it has to be designed for the whole body. When choosing a shirt and pants, you can pick out the size that correctly fits your upper body, and another that fits your lower body, but with the jumpsuit you can't mix and match like that, and a poorly fitting jumpsuit is a problem because it can restrict your body movements. This makes it harder to pick out a good fitting jumpsuit off the rack.

A jumpsuit can be a problem when going to the bathroom.

Jumpsuits haven't really been in style since the early 1980s.