Not OP but here’s one use case. I use FF as a PDF reader, it’s faster than Nitro and Adobe opening files and searching within. When I have a 600+ page Admin Guide open scrolling is prohibitive. When I do a text search FF puts location indicators in the scroll bar. A larger scrollbar is better visually and easier to interact with.

Also, what kind of psycho uses a touch screen on a desktop computer?

One that uses Firefox with ublock origin for the internal browser. Coming from Relay for Reddit, I find opening external links in the stock chrome browser to be extremely painful.