1) Because I'm cheap. Just wanted to get that out of the way right in the beginning.
2) Because as a single person, I tend to think of weddings as funerals because they actually have a lot in common. Your whole family is there. Your friends come. People cry. There's food. More often than not its at a church. And most importantly, when you are single, you'll never see those people again until you are on the other side.
3)Wedding presents are for married people to give to newlyweds to welcome them to the neighborhood of married couples. They're always excited to get some new blood in to teach that high school aged Sunday School class and inform them of what kids are up to these days. Always looking for potential new couples to invite over for shared dinners and whatever else married couples do for fun.
For a single person, its really a going away party. You don't give presents at a going away party, generally, at least I don't. You wish them luck and promise to stay in touch, although that doesn't happen too often. Honestly, people getting married ought to give presents to their still single friends. First, as a consolation prize for still being single, but secondly, which of us single folks couldn't use some new dishes or a new set of towels. I could use a crockpot just as much as a newly married couple could. I thought the point of getting married was so that one of you could cook for the both of you. I don't have anyone at home fixing me dinner for when I get home.
So if you didn't get something from me, don't worry. Its nothing personal.