Why do we call it a restoom when no one in their right mind would rest in a restroom?

FACT
Restroom is synonymous with washroom, public toilet, comfort room, toilet room, and bathroom. Some of these rooms also include a fully operational bathing facility such as a bathroom would have. But still the name restroom remains a bit confusing. More often now you will find, in North America anyway, restroom and bathroom used as the term for a public bathroom type facility.

Restroom and bathroom originated in the U.S. and they are the most prefered terms used in Canada and the U.S.. One Reason we have strayed away from saying bathroom in public areas is because bathrooms usually will have a bathtub as well. Public restrooms will not usually have a bathtub. If they did, I'd be slightly worried.

British folk have trouble with the word restroom simply because they remain hygienically confused; generally because people with quasi decent hygiene don't usually take a rest in a restroom. Hence the reason why it really shouldn't be dubbed "restroom". For the British folk, they still prefer bathroom as a general term for the poop-er. Still we all remain hygienically confused with the term restroom in the U.S. and Canada!