Bush's college records were leaked by somebody at the college. Bush figured he might as well have them officially released.
Kerry's college transcripts were part of the military files. McCain's ranking at Annapolis was a matter of public record.
President Trump released his college records.
We know what President Trump studied and that he graduated, but we haven't seen his college transcript.
But generally politicians don't release their college grades. Why would they? They have nothing to gain from it and much to lose. There's even less incentive for a politician who's left office to reveal his college record.
What would Obama's transcripts show? That he got so-so grades, some good, some bad? That he wasn't a genius and wasn't an idiot?
If you really think he got a degree without doing any work, he probably won't have any trouble coming up with a fake transcript. That can't be any harder than getting a degree without attending classes or doing the work.