Actually, ReactOS and Wine have historically worked together and share significant technical overlap in the goal of reimplementing the Windows API, though they have different approaches and end goals. They're separate projects now, but a lot of work in wine happened thanks to ReactOS.

because a fucking depressing amount of computers are still running old windows versions for compatibility reasons, and it would be really nice if we could eventually replace it with something that isn't a leaking sieve in terms of security.

why would you try to copy windows?

Because you may prove you can? I mean, this is an absolutely valid reason.

Never underestimate a dev's willingness to do something simply for the hell of it