Just take a look at all the variations in this HN thread on the spelling of it. "Pop", "PopOS", "Pop OS"... I only counted two that used the full name "Pop!_OS".
There you go. "Windows" has been the most consistent in its original naming and is instantly recognisable on its own without the versioning names (XP,Vista,7,8,10). Ubuntu is also the same.
macOS was nearly confusing (was first Mac OS X, OS X and now macOS) but is still recognisable in the software ecosystem with its exact full name still used.
The name "Pop!_OS" on the other hand looks so cryptic that its users have simplified the name to just “Pop OS”. It’s likely that someone will create a distro for the sake of renaming it. I won't be surprised to see a renaming soon.
FWIW I work on Pop OS for System76 and using the "proper" name doesn't really matter to us. I don't even use it myself, except when I'm writing technical, first-party information/documentation that needs to be part of our cohesive brand. In colloquial use, just call it Pop.
Agreed, and it's a crying shame, because over the past 23 years of trying and using Linux distros for work and play, I find Pop!_OS to be the best of the lot by a wide margin. I don't imagine I'll use another desktop distro on any of my systems unless System76 somehow screws up all the fantastic work they've done on it.
macOS was nearly confusing (was first Mac OS X, OS X and now macOS) but is still recognisable in the software ecosystem with its exact full name still used.
The name "Pop!_OS" on the other hand looks so cryptic that its users have simplified the name to just “Pop OS”. It’s likely that someone will create a distro for the sake of renaming it. I won't be surprised to see a renaming soon.