Alcoholic beverages are not permitted at the Philadelphia Folk Festival. It's something to do with the law or liability or the plethora of lawyers. (An attempt was made, this year, to have a beer tent near the food venders but it didn't work out). This does not mean that there is no imbibing at the fest. The thousands of campers enjoy whatever refreshment they bring with them. So long as they are not dragging kegs into the campground, the powers that be turn a tolerant eye. I am keenly aware of the booze ban. For thirty years, I ran the big campfire sing and each night I began the procedings with a reminder of the rules and an offer to "dispose" of any contraband (potable or combustable) from penitant souls, no questions asked.
I have played at festivals in U.K., Ireland, Israel and the USA and they are different, reflecting the cultural mores of the country. Americans are more into picking sessions than singing sessions. Our love affair with improvisation is evinced in the popularity of such forms as Blues, jazz, rock and bluegrass. Our European fascination with precision and tradition has been tempered with an Afrocentric response to rythmic variety and complexity. I'm old, so I was raised with Eurocentric values (It's why I became a folksinger) but I am, also, American and I love to play swing and bluegrass and to alter melodies as I go along.
The biggest difference between European and American festivals is the attitude toward tradition. Americans are not as in love with their traditions as you guys are. There are many possible reasons for this (Age, political awareness, ethnic multiplicity. etc) but the fact remains that, without a strong tie between the audience and its roots, a folk festival is nothing but a music festival in jeans.