..or it's just easier to embed your one single Webapp in a desktop app while caching some assets. So, shared codebase? But yea, also a lot of web devs for sure.

TCL never got any other toolkits. There have been a few TCL/GTK attempts, but I think all of them went unmaintained. It also doesn't help TCL doesn't really have objects .. or .. keywords. I don't think it would scale up to big projects well.