That would be awfully convenient. You'd never lose them or need to deal with another native application. Just open any web page that echoes all HTTP headers and then check your account balance.
Or maybe having a separation of concerns for different applications in a general purpose computer is worth the friction.
Upon further research, I have found that I misread the word "unnecessarily".
Personally I prefer to use a separate, dedicated service to run my language models, and I bounce between a few clients for various things. One of them is a (local) web interface (open-webui).
When you use an LLM, you provide it context. Where do you usually get that context from? Some service, JIRA, whatever, in your browser.
A browser is one thing that users will go out of their way to replace, making it a pretty attractive vehicle for stuff like this.
Why does my browser have a PDF reader and print manager built in?
Opera has been bundling stuff like that, even a BitTorrent client, even when they were still a Norwegian owned company.
No longer the case since they switched to Blink. Nonetheless, Opera still comes with more built-in functionality than other browsers, such as ad blocker, in-browser VPN, and builtin ads occasionally.
GenAI on the browser skips the intermediaries and probably loads faster than all the JS needed for 1200 analytics "partners" and reinventing the wheel badly by making it load text on the fly based on your scroll position rather than letting the browser handle it because someone just assumed a few thousand lines must be slow and never stopped to try it.
Plus it being local means it might even work when you have no signal.
Opera has historically been a junk drawer of technology. A BitTorrent client. A mail app. A chat app. A web server. There have been innumerable features which were often unnecessary or puzzling. It does not surprise me at all to hear that they're adding local LLM support.