LOL! Gotta love bars!
There is a more serious reason I use "ungrounded" extension cords and power strips. We were doing sound re-enforcement for a benefit with several bands, and three of us got all our DJ equipment together for as much wattage as we could put together. It was at an Amvets hall, and this building has really old wiring (I'm talking 10-amp fuses - yes, fuses).
Naturally we put each set of amps on different circuits (well, different outlets, guessing that they were actually different circuits).
So we have the main DJ mixer that needs to run to the main audio board, for in-between music while changing bands. As soon as we connected the audio cable from the DJ mixer to the 32-channel main mixer, everyone in the room plugged their ears and ran outside. It was the most horrible 60-hertz buzz at several thousand watts you ever heard, for about 5 seconds before the magic smoke came out of John's mixer.
What happens sometimes in older buildings is that an outlet is wired backwards, and since these older buildings don't have a separate "earth" ground, the ground prong is tied to the "common" lead. Except that if it's backwards, the ground lead is actually hot, 110 volts. Patching that audio cable essentially sent 110 volts through the audio.
Luckily it was John's $150 Karaoke mixer that fried, and not the very expensive 32-channel console! We had a backup mixer, so the gig went well aside from scaring the bejezus out of everyone during setup/sound check... he even got reimbursed by the hosts, as this was a volunteer benefit.
Ever since then, I simply refuse to connect to someone's Earth that I didn't wire

Even connecting your video cable to a TV on a different, improperly wired circuit could cause damage. And in reality, those 2-3 prong adapters aren't perfect, as the little ground tab can still touch the plate screw...
But again - none of us here are recommending this practice!!! If you are holding a mic and touch anything that is grounded, and your system is not grounded at the same potential, you can get a hell of a zap... so take this simply as anecdotal and not as advice... proper grounding ensures that there is no voltage difference between any two devices and is in fact a safety feature if done right.
But again, remember what kind of people often pass as electricians in some of these bars... and bar owners love to save money...