Why can't ExpressVPN connect to browser specific extension only

So i have been using VPN’s for years and recently tried ExpressVPN. I had to uninstall it after about 1 day because it just can’t connect via browser only which is extremely stupid for a company as big as ExpressVPN. If you want to use the browser extension you have to use the desktop app. I mean seriously? Why is there EVEN a browser extension when you still have to turn on desktop app?

I have used NordVPN, Cyberghost, Windscribe, surfshark, hotspotshield to name a few in the past and they all do this. I never even bothered with their desktop app, just download the browser extension and use away.
I tried split-tunneling and other options but it just didn’t work and i am not willing to spend hours trying to figure out the connection for a VPN which is the MOST EXPENSIVE and doesn’t provide any real benefit over say nordvpn.

Let me explain why i want this, say if i want to stream disney+ and workaround country restriction i just want to enable USA server through my firefox, i don’t want to route my whole traffic through USA and getting logged out of my applications like steam/battle.net because suddenly they checked my IP has changed to another country.

Which providers have you found that support browser only VPN?

Almost all of the vpns i listed support that.

Windscribe, Surfshark vpn, Nordvpn, hotspot shield are to name a few that i have used recently (in 2021) where you can login to your account directly via extension and never have to install the desktop app if you don’t want to.