The 10 year old PC has a much much bigger power budget than a phone. It wasn't until really recently that ARM got anywhere close to x86 performance.

While the phone technically possibly could be better, it would also drain in an hour or two if it was maxed out. And most people have crappy phones that can barely hold 60fps doing nothing so mobile games usually target the lower end devices to maximize the amount of potential players, while also remaining battery conscious.

There's also just not that much demand. Nobody has space on their phones for a 120GB game, and nobody wants to play a AAA game on their phones because gaming on a phone sucks ass and if you're going to dock the phone you might as well get a console.