doesn't ChromeOS has a built in SSH terminal? I received a Cr-48 (original beta) and I remember that was the feature i used the most

Yes, but it's a pain to use in comparison to this.

I'm curious: Is there any use case for this beyond Chromebooks?

It is a nice alternative to Putty on Windows

Yeah, I've yet to find a good terminal on Windows.

I only use a web browser and a terminal on OSX.

Often I want to repeatedly swap between a terminal and a web browser tab - for example, when developing a web application.

Having them in the same tabbed window might make the workflow, and division of my windows, more natural.

Another example - I use mutt for email in a terminal. So if I'm writing an email about a web page, I might prefer it to be in the same window (different tab) as the web page.

Downloading now to try it out...

If it's easier to have your terminal in a browser tab than for it to be a separate application, that is a major failing on the part of your window manager (or at least your understanding of it).