Because Firefox on mobile is a pile of shit to be honest. It works great on desktop, but the mobile experience is subpar. For a chromium browser, Bromite used to be an option, but it seems abandoned now. Brave is one of the few Foss chromium browsers left that also supports adblocking.
Really? Who would’ve guessed that piracy is a service problem? How about you improve your shit so people don’t feel inclined to pirate it. Who’s gonna pay for a shittier experience?