A few thoughts:
If you can play the instrument you're sitting behind, it's just a matter of taste.
I was playing an Irish wedding (in Kent). When we arrived, the thirteen piece jazz band was just leaving, and Granny was absolutely rat-arsed. At a break in our set, a beanpole of a Mayo man lurched up and said, "Can you play a double jig?" As we started, he kept saying "slower, slower..." until we were going dotted crotchet = 60 or less, whereupon he kicked off his shoes and treated us to about four minutes of the most amazing dancing I have ever seen, then just stopped and walked off.
"Because I can" is just showing off.
I once had a bollocking from Rod Stradling (what does he know?) for playing English polkas too fast...
And I play at our local steady session for beginners whenever I can, 'cos it's passing it on. If that's patronising, remember that patronising used to be a positive word. There used to be people who went there to show off; to the eternal credit of most of them, that's now stopped and they are really supportive. It's an old fashioned concept, but good manners are still important.
End of sermon...KYBTTS