There historically has been a lot of reluctance to. And there was a lot of dirty campaigning in the primaries. Like what you’d expect in the general normally. Not to mention there’s been a lot of baseless neoliberal pearl clutching, not strictly related to this in particular that’s already getting ugly. It was never a given they would concede magnanimously. But so far it seems they have. Which is good. Hopefully the sooner people like James Carville or Bill Maher switch their registrations to Republican. The situation will only improve.