I didn't walk either. I don't have any regrets about it really. I went to see a friend graduate a year or two ahead of me and the main ceremony felt like a huge formality and was extremely impersonal. There were inspirational speakers telling you nothing you haven't heard before, announcements of honorary degrees for people I did not know, a speech given by the class representative (who spoke more or less about the experiences he had with HIS group of friends) blah, blah, blah. Then there were the departmental ceremonies where you actually get your diploma. I opted out of that one too, but I know people who skipped the main ceremony and attended the departmental ceremony in order to get their diploma.
I guess the main reason for my not attending graduation was that there wasn't much "spirit" or feelings of "togetherness" at my school, and I thought that that was what really made graduation feel good. Also, a lot of my really good friends graduated a year before me. I graduated in four years, but for some reason I didn't have any strong bonds with the people who were in my class, just a bunch of acquaintances. At my university, people graduate all over the place; it's very common to do a fifth year if you're double majoring or switched majors, and for the more intense majors, people take 6 or even 7 years to graduate. So class cohesion does not really exist. So I didn't feel like it would be a big deal to not walk with my class.
So I say that if your parents do not care if you walk or not, then go with your own feelings on the matter. And if you decide not to walk, you're not alone! Just make sure you really think it through and are happy with your reasons, and saying you would rather play PS2 is not a good reason!