You're just seeing the massive glut resulting from the training and staffing trying to capitalize on enteprises going web-based to try and reduce employee costs.
There's a lot of jobs in backend systems and services that, while networked, have nothing to do with the web. They tend to go to more experienced, specialized engineers.
I had similar thoughts a few time ago and you are not completely wrong. Android devs usually see web devs as something completely different but the truth is... complicated . Actually its all related to internet.
The internet is the biggest thing that happened in tech in the last 40 years and has grown so much that their are different domains and careers around it. Backend, frontend designs, frameworks, db admins, cloud engineers... These are the skills that run the internet and therefore there are special careers in for the people that work on those
But most of the time the knowledge require for such skills overlaps with each other at the earlier stages. (For eg js is a messed up shit used by almost every one for everything ) Thus the people you are referring to as "web devs" are those people with either specialized or general knowledge of how the internet works.
Android is just 11 years old and is more relatable to frontend side of a web dev or systems side of OS dev.
Wisecrack407235dweb has really come a LONG way in terms of making interfaces and front ends *just* the way you want them.
and if you're working ever green browsers only, you can afford to stay as far as fucking possible away from all the bullshit they call "transpilers" like babel and all that shit (more like transpilesofshit) that come with "helpful" things like instructions to install 5 god damn GB of dependancies, some of which always fail because of some stupid fucking path issue or dumbfuck node ver conflict. have 700 fucking critical vulnerabilities, will e-beg you ON The FUCKING CONSOLE to donate to projects, will be fussy like a god damn child and take a fucking hour to get the configs right because everyone who makes this shit apparently was born believing convention is for retards and why not throw out all docs or standards and let anyone do "anything!" instead of having some sensible fucking defaults.
but plain js and modern css are something to behold sometimes..from a distance.