Frequency is definitely a factor, and then there's dementia, oh and senility, and did I mention frequency? ..........Oh and dementia comes in there somewhere.....

But having a good chorus helps, like in 'On 'is 'orse with 'is 'awk in 'is 'and.

Seriously if a piece is genuinely funny or irreverent in some way, and you don't hear it every day, there are many people myself included, who love to hear it over and over and join in the punchlines. Some of the monologues, like Marriott Edgar's, I never tire of, and those related by John Cocking.