Never been on one either, but only weddings i've been to are relatives (nephews, etc.), and i REALLY don't get the uncles & dads joining the stag do. Was in Krakow recently, and the number of pissed up Brit stag groups in the city (and especially the airport coming home) made my skin crawl. Polish police gave them short shrift too, as it is illegal to drink in the street.
When i got married first time, was just a pub crawl with a few mates. Second time 5 years ago me, the wife to be, her bridesmaid and hubby, and my best man and missus went to a Greek restuarant the night before the wedding, and we had a great time.
Dull, maybe, but memorable for us.
I just don't get the overseas stag/hen weekends! But each to their own.