I went around Aberdeen, Edinburgh and Strathclyde on their Engineering open days and never had my parents there. I just got the Citylink to these places and back but if it was somewhere like England where it's the parents forking out a few thousand pounds each year then I could understand the will for them to come along.
In Scotland however, if you're big and bad enough to go to uni by yourself for three to four years then you should be able to get there and have a look around by yourself without someone in your ear or you feeling pressured to ask the 'right' questions just because your parents are there. If anything, I'd probably be more likely just to shut up and ask less if mine were there.
I thought the same thing when I saw all the parents walking about. Looking back on it, I think my mum rathered I went to Strathclyde rather than Aberdeen (my eventual choice) so that one decision to go by myself could have changed my life path