Almost every portable and ultra portable typewriter made from the 1930s onward came with a case that the typewriter locked into. On almost all of these the top of the typewriter case was easily removeable from the base with a spring loaded locking mechanism of some sort. This allowed the user to sit in almost any chair and use the typewriter on their lap. The thin case bottoms prevent dirt and oil from soiling one's clothes.

Beginning in the late 60s/early 70s some manufacturers began making plastic tops that clipped onto the typewriter bodies, but often these are more brittle and prone to breaking/shattering due to the type and age of the plastic. (I'm looking at you Remington Streamliners...)

Our cat used to love "hiding" in the wooden case tops of my 1940s and 1950s Smith-Coronas (Clippers, Sterlings, Silents, Silent Supers).

It's really only the larger and much heavier standard machines that didn't come with cases at all.

Typewriter Video Series - Episode 74: Choosing Typewriter Bags by [[Joe Van Cleave]]

My first "ultra-portable" (Skyriter 1955) by [[Just My Typewriter]]

55 had an integral cover versus later versions which had bags.

Typewriter Video Series - Episode 143: Rocket Versus Skyriter by [[Joe Van Cleave]]

Typewriter Video Series - Episode 121: SCM Skyriter by [[Joe Van Cleave]]

Joe likes this better than the Hermes Rocket. Solid ultra portable.