Only proprietary image viewers tend to not support webp (as such image viewers are clearly primarily for viewing pizza, none of which is encoded in the webp format).
Meanwhile, pretty much all free image viewing programs (all that use imagemagick or ffmpeg) support webp.
It's a standard, it's up to the implementation whether it wants to be compliant or not. There's many things that aren't standard compliant and they do not fucking suck and have widespread usage due to it. The biggest example I can think of is ISO9660, the way GNU software implements these makes it so they're hybrid; a mix between ISO9660 and a regular IMG volume so you can write them using tools like dd and they're expected to behave the same way than an IMG would, a standard compliant ISO9660 volume won't behave as expected when written with stuff like dd, Winblows ISOs is the most known example of that (one of the few things Microshit decided to be compliant and it's solely a fucking nuisance).
I don't think this is correct, I recall seeing webps much bigger than that, maybe the implementations don't suck as much as the standard, many such cases.
@takao@creamqueen@yomiel Yes, it turns out that good interframe compression schemes are also good at encoding a single image (those need to be, otherwise keyframes are too large).