In the late 1980s there were a lot of sitcom episodes where the characters discover a forgotten blues musician living nearby. Have you noticed this?

The musician was usually not playing anymore and the characters would have to convince them to put on “one more show” to make the guy happy again.

This story can be found on Family Ties, Facts of Life, and Doogie Howser.

Was this kind of story going on in real life, where a lot of blues musicians were forgotten by the 1980s?

Also there must be a few other sitcoms that had a similar story, does anyone know any?

I don't recall blues singers specifically, but by that era there was some public discussion of early R&B and jazz musicians not having any royalty rights to their recordings, so that they were living poor in their old age.

I think the sitcom plots might be an update on an older theme. The Partridge Family did something similar with a white folk singer (played by William Schallert). Dick van Dyke Show with an old radio star played by Richard Haydn.

Not a sitcom, but Route 66 featured an episode about an old jazz singer.
Goodnight Sweet Blues might fit your criteria.

If I can include dramas:

Matlock (The Blues Singer)