I don't know
I too have 100+ neighbors (not all of them active, but I still recieve 20 maps per day, so no complaining here), and NEVER visit, as my device may crash. My wall is very silent too, 1 or 2 messages per month
I don't need the coins, just need neighbors for exchanging gold and maps.
But when you're a beginner, you can definately use the 250 x 5 (dunno how many dragons you can play with, lol, this shows how long it has been since I stopped visiting) coins each visit gives you. And some players are very social players, and find friendships through their walls.
Anyway, not my type of playing this game