Thin Lizzy did it because they were out of Ireland and needed a B-side (which became the A-side) and they wanted to "put it out for a laugh, for the kids at home. "

Metallica did it as a specific homage to Thin Lizzy whom they recognize as an influence in their own music. Garage, Inc. was a release of songs they used to do as covers when they began...they did not alter Thin Lizzy's version to any great extent...

At any rate, I'm not sure it really has that many more remakes than say Danny Boy or other Pub standards...its just the popularity of first Thin Lizzy and then Metallica's release.

That said, I dig the song...drinking, fighting, prison, brothers, a dishonest woman, add a dog or a pickup and it could hit the country charts