> Is this a legacy thing or does a tilted cursor serves a purpose?
It's not just a question of historical fact. There's where it originated from. Then there are the documented reasons they first did it that way. Then the undocumented but plausible reasons it started that way. Then there are the reasons it has stayed this way. Those reasons aren't facts, they're counterfactuals.
Implicit in asking why the mouse cursor is like this is asking why it isn't a different way. If there was a better enough cursor, it would have won out. So all of its reasons of functionality, even the ones the inventor didn't think of or didn't matter historically, are part of why it is the way it is today.
It's not just a question of historical fact. There's where it originated from. Then there are the documented reasons they first did it that way. Then the undocumented but plausible reasons it started that way. Then there are the reasons it has stayed this way. Those reasons aren't facts, they're counterfactuals.
Implicit in asking why the mouse cursor is like this is asking why it isn't a different way. If there was a better enough cursor, it would have won out. So all of its reasons of functionality, even the ones the inventor didn't think of or didn't matter historically, are part of why it is the way it is today.