Yes, Keith, of course people should learn the songs/tunes at home. Some people are natural performers, but for others singing in public is a big step. You can sing a song perfectly 50 times in your bedroom, but it doesn't mean you can stand in front of an audience and remember the words! I have noticed that, on occasion, people who persevere are rewarded with greater applause than others who put on an, apparently effortless, polished performance.

As for songs no longer heard in folk clubs, topical songs can have a relatively brief life-span. Tom Paxton has written many songs inspired by news events - what he has called "short-shelf-life songs"- although sometimes topical songs take on a greater significance. I haven't heard any songs about Viet Nam, nuclear power or abortion recently. Anniversaries - the death of Jean de Menezes, for example - may bring some once-familiar songs back.

But any song you mention is likely to bring a response of, "I heard that last week!"