Quite the straw man we've constructed here.

I am the exclusive user and I only watch from browsers on laptops and desktops attached to whatever display and audio outputs. I suspect this describes a non-trivial portion of the audience here as well. I don't care about someone being able to watch my media collection on Xbox because I don't have one.

> I am the exclusive user and I only watch from browsers on laptops

People doing that don't need a media server like Plex or Jellyfin, you just need a directory on your computer. People who use Jellyfin or Plex have a very different case of running it on servers, then streaming it to TVs, streaming boxes and mobile devices.