It allows using the browser as a very convenient and accessible programming platform for many types of applications, not only web-based. That's specially important for beginners, I think, as they can run (and create) all kind of projects just by opening a web page. But it is also very handy for more advanced users, as the wled project [1] shows.

And yes, there are security implications. But that's true for any other platform and as long as the users are asked for the proper permissions, I'm good with it.

[1] https://kno.wled.ge/