This one is so common at my gym that I have trouble finding me someone who will give a good spot. I tell them not to help me, and that they are there for safety only in case I can’t finish the last rep. Somehow they think this means they should do some deadlifts with my bar at the same time I’m benching. Some of them will start “helping me” when I’m about half way through a set (that I usually can finish myself with no help). They are so used to lifting significant amounts when spotting and/or needing significant help themselves, they just don’t even think about it.