And I don't know if it's because alcohol seems to be at all events, but I've yet to witness anyone getting totally drunk at a wedding.
You're lucky if you've never seen drunk people at a wedding. I had the misfortune of being a bridesmaid for my friend several years ago. They had an open bar and three of the guests and the Maid of Honor got very, very drunk. The MOH gave some rambling toast that made no sense because she was plastered. Then she got into a fight with her drunk date and the police were called to the reception hall! Then one of the girls who was wasted threw up on the floor and the bride walked through it, not realizing someone had just thrown up in the middle of the floor, and got it on her gown

If it's a question of open bar vs. cash bar vs. dry reception the bride and groom should just go with what they are most comfortable. I've been to several dry receptions (usually for religious/cultural reasons) and had just as much fun as an open bar reception (but I'm not a big drinker). People who matter to you and want to celebrate with you won't care that you're not serving alcohol. Personally, IMHO, a cash bar is tacky.