Every time I'm back at the course I grew up playing, I watch all my dad's buddies - who've been playing this same course for more than 30 years - look for yardage on sprinkler heads, every hole.
I guarantee if you took the numbers off the heads, these guys would be forced to dig into their memory banks, and they'd know exactly how far they are from the centre of the greens, all day, without referencing a single head.
Yet, there they are, every round, almost frantically looking all over the place for markers on approach to the greens. Odd.