JeDaYoshi
Interesting one - I generally found it to be the other way for me. Chrome was sluggish on my older phone, but Firefox was faster.
Outside of the points that Scotty made, not everyone has access to a computer, or don't have good enough ones to handle streaming as smoothly. In fact, there are multiple use-cases for this technology, considering it can work as a "cloud browser", either storing information or being completely disposable (as in, the whole browser activity/session/data gets destroyed after usage or on-demand). That said, for what we're used to, a lot of people use it for watch parties so they can share "a bit of the Internet" between friends, family, and even completely strangers!
And I say "we're" because I work on a similar, open-source, "Rabb.it alternative" (or VM-sharing platform, however you prefer to call it): https://cryb.app
That said, that requires self-hosting, so feel free to check out Hyperbeam if fiddling up with configuring Node.js applications and Docker apps is not your thing! But if you wanna give yourself an adventure for this use-case, go ahead :)