Hmmm - not balding (yet) and I don't drink Guinness, but other than that the only answer I can come up with to your question is "Because we have taste."

(An alternative answer is that we can't sing either, but distract others from this by our beards, hippyish appearance and the glare from our foreheads and eyelids.)

Incidentally - the New Lost City Ramblers always used to perform in suits, because they felt it was how genuine old time musicians would dress if THEY were playing large concerts.

As to the last line of songs - this is a very old tradition in ballad singing. I have a recollection that it comes out of Irish musical traditions, but I'm not certain. It's been a long time since I took that college folklore course. Many field recordings have this stylistic element, and many revival singers of traditional songs like to perform as "authentically" as possible.

Dan Schatz and his beard.