leaks are like game demos, they can generate hype and boost sales - if the game is actually good (or gets meme'd enough).
but it doesn't work at all and has the opposite effect if the game is crap or just reinforces what people already think about it.
sure, you might get some contrarian sales (which most likely would've bought it anyway), but the big mass of normies who only buy the game based on NAME and REPUTATION will stay away if that name is suddenly associated with being shit. they don't even have to see it themselves, they just need to hear their peeps or the internet at large talk about it.