It's a social lubricant, the equivalent of sharing a match to light a stranger's cigarette. When chart-watchers at Morgan Stanley meet the fireman union rep in the bar, work gossip won't do. Meanwhile you wait for him to stop talking so you can dump your canned laugh into the conversation pot and get the damn thing over with. So you have to laugh at that one too to spare the new guy's feelings. Even worse, you may feel the need to join the merriment with a contribution of your own.
Wit is different.
Wit blooms when a personality reacts to the ordinary pass of life. Jokes consist of bland personalities caught up in wacky situations. There's a 478-word joke on the Web involving some 'wacky' set up about a couple vacationing in Transylvania. I assume it's intended to be funny, but there have been death marches with more sprightly wit. The author is unknown, which is lucky for him.