My doctor told me that sometimes it's just genetic. My dad had them when he was in his 20's along with varicose veins, and he was very athletic in that tall, skinny, swimmer/runner sort of way. His short, curvy sister who never had children got them, too. My brother and I have them, and it started young for us, too. Thanks to my dad, we've always focused on fiber in our diets, so I don't think it's that. I don't think western-style seating helps much, either.

I also am surprised at how many people on this forum are sharing their experiences. It's not really a subject for polite chitchat, is it? Maybe that's why seems a lot of cyclists experience them. I think more people than commonly believed have them. They just don't bring it up.