Its because white cant win anyways, black doesnt have enough material. White could try to put the black king in zugszwang but if white makes any move black is either preparing to take the bishop or load up on the pawn, at any given moment black can sacrifice the bishop for the pawn. So this position is a draw because of insignificant material essentially. You cant remove the black king from its current square in time.
Today I was playing a game that was bound to be a draw and I got a brilliant out of it. Can someone explain this to me because I feel like this is an error on the engines part