It's a carry over from live plays and shows where people would laugh in the audience together during the show. They basically just started filming them on camera and then started making them specifically for that new technology known as TV. Some people like an audience experience, some don't, but a lot of people grew up with that as the standard so find it familiar. It's only been fairly recently that they switched to someone looking straight down the barrel of the camera to replace the laughtrack.

> It doesn’t affect my reaction to the joke that has just happened

It does affect your reaction to a joke. You just don't realize it.

It's an important reason why people have the ability to laugh. It's signal to other people to find something funny.

(Of course, if you have a personality disorder, you might be immune.)

You might not like shows with a laugh track, but that is a different matter.

The important thing to understand that is that multi-camera shows with a live audience (that is told to laugh) or a completely fake laugh track is made differently.

The script and the performances actually have pauses build in for the laugh track.

Actors time there performance because they know the laugh will be there or will be edited in.

And arguably multi-camera shows need laugh tracks because without it they come across as awkward.

In case you are wondering, the multi-camera approach is fast and cheap, which is why it's often used for sitcoms.