Absolutely 100% about visual appeal.
Shots where the stairs are covered aren't as cool, because there is less consequence to screwing up.
Now... I'll also add to that though that when you do a trick with more consequence, you actually tend to do a better job. So if you shovel those bitches off, and do it like a real man... you have a higher chance of sticking the rail, because giving up like a little bitch would result in a 'stair massage'.
I used to rock climb, and my buddy who taught me always harped on a very important lesson:
"There is a drastic difference between letting go, and your fingers literally exploding off the hold because you found the edge of your bodies capabilities. If it counted, the first would mean you're fucking dead because you're lazy... and the second would mean you gave it everything you have.'