They are racking up click-throughs.
Advertisers pay just as much for accidental clicks as intentional ones, so the site operator is incentivized to generate as many as possible. Being the dumbest morons ever to mo a ron, the advertisers don't understand that they're the marks in this particular con game.
Eventually they will get tired of paying for worthless clicks, but I wouldn't hold my breath.
They'll just start paying less per click. A worse outcome for everyone, not just the bad players.