On observation of tap use of debit cards, I see them almost always defaulting to PIN first. Sometimes, you can bypass by hitting a key (enter or green) and the transaction goes through PINless. Other times, it cancels out.

For the life of me, I don't know why debit/cash places enforce PIN when there should be no difference between that and no PIN in processing fees. I know some here like PIN, but... Also, almost all debit cards have a MC/Visa dual link (aside from the fact that MC/Visa bought most debit only networks awhile back). I can't imagine there is cheaper routing for debit with the existing laws in the US in place.