but the pros can't, correct ?
They can use laser rangefinders before, but not during the tournament.
Anyone can get the right distance with a laser, but how many can actually hit it that far, accurately? The caddies on the tour walk the course before every round, have a book with course details and distance to the front edge from sprinkler heads, water pipe covers, trees, the edges of bunkers, etc- they're able to look at the book, get the yardage and then, it's a matter of adjusting for wind, course conditions (dry, medium, wet) and humidity.
I prefer to do it the old way- use the markings on sprinkler heads, walk to the ball and add/subtract before picking a club.