When you learn nothing about his hand on the turn we cant call the river. He doesnt have a straight, id bank on that, but what we dont know is if we are picking off a weaker ace or a dummy with a set who either cant bet turns or misclicked. Hence we need to fold to a bet that size on the river without a strong read opp holds a weaker ace or some missed draw whic hwe have no clue about.

If we bet $8-10 on the turn and a super-passive raises us on two streets its insta-muck time without a set.