What is the use for this? I mean how many people actually use such tools for actual day to day dev? Maybe for some quick edit if you don`t have laptop/computer at hand, but otherwise I see no real advantage of this.
> how many people actually use such tools for actual day to day dev According to an Xoogler acquaintance, he used a web IDE for all his development; I'm not sure how widespread this is in Google, but the answer to your question could be "lots". (Any Googlers want to chime in with estimates on % of devs using web IDEs?)
It helps that there's a single source repo to work from, a remote filesystem for all source code whether working remotely or local that syncs immediately, and a single build system.
For me, I do all work from my laptop in the web IDE and save harder or larger things for when I'm at my desk. It's pretty great that I can start a change in one, then switch to the other seamlessly e.g. write the bulk in an IDE, then make changes in response to comments via the web IDE.