...but there are TV shows (america's funniest home videos, for example) who's stock in trade seems to be...

Even though they have an audience I'd wager against the producers relying on *them for the sound of laughter.

It's the same reson why, IMHO, most feel "Sienfeld" or "Freinds" are funny... developed consumers of comedy being propped up by the use of laugh tracks.

Spelling altered to protect the innocent.