I, and most people I worked with, couldn't care less if the border/title bar looks slightly odd, the same happens on Windows a lot.
The issue ain't different WMs or toolkits, but a lock-in effort from Microsoft with HW and SW vendors, they still had to create WSL to actually improve their dev experience though, could not manage that without.
Most people ain't technical experienced or interested in IT and just don't care enough to actively switch their OS, so they use what's shipped with it, if it was a Linux Distro they would just use that.
I am yet to bother with WSL, it hardly brings something I wasn't already having with VMWare and VirtualBox, and in any case "developer != UNIX".
The cleverness of WSL is that Microsoft came to realise, thanks to Apple, thank many folks only care about having a POSIX userland and don't really care about Linux as such.
Given that current generations mix up Linux with UNIX, it made more business sense to add Linux compatibility than revive SUA.
So now those folks mostly jump between Apple and Microsoft platforms instead of supporting Linux OEMs as they should in first place, genius.
It had to be not just any POSIX userland, but the kind that could run all the popular web dev tooling, starting with Node.js. MacOS can get away with not being like Linux in many ways because of how widespread it is, but a new contender pretty much has to be compatible. And Linux is especially convenient to emulate due to its public and stable syscall interface.
All that said, the kernel emulation layer that WSL1 was built on was originally intended to run Android apps.
Node.js runs on many things, but packages (which is the actual thing that people want) are another matter. I remember trying to npm install something on FreeBSD; you wouldn't believe how many package scripts straight up assume that /bin/bash is always there.
And yes, Android apps are already there on Win11, so it kinda came full circle. But either way, the point is that emulating Linux kernel was originally a choice made for the sake of Android compatibility. That it ended up providing a much-needed development environment is a fortunate side effect of that decision.
The issue ain't different WMs or toolkits, but a lock-in effort from Microsoft with HW and SW vendors, they still had to create WSL to actually improve their dev experience though, could not manage that without.
Most people ain't technical experienced or interested in IT and just don't care enough to actively switch their OS, so they use what's shipped with it, if it was a Linux Distro they would just use that.