Signposts help. I can think of a couple of places I'd never have seen if the signpost weren't there.

It's probably especially useful for cardriving folk. It helps avoid the 'blink and you miss it' effect if you know what surrounds the sign, you are primed to spot it, and to not zoom past, finding that you can't turn around for a couple of miles. I don't drive, but have been a passenger enough times to see this effect in relation to old stones and stuff.

I can also think of a couple of places I wish did have better signs. We once circled Stanton Moor about three times (possibly widdershins), finally giving up and turning around at the spot where we should have stopped. That was in the days before geordies were allowed to use OS maps outside Newcastle.