I think sports are just one of the many, many facets of a particular locations culture that some people happen to be very into, and some people don't.
I think knowing that certain sports exist in your own country is about as far as a person "should" be expected to know something. In other words, as an American, I "should" know that football is a sport that kind of only exists here, that what we call soccer is what everyone else calls football, and that most places also play baseball and basketball.
I consider that to be the same level of knowledge as knowing that Ella Fitzgerald was a jazz singer, or knowing that F. Scott Fitzgerald wrote the Great Gatsby, or knowing that George Gershwin was a 20th century American composer.
But as much as I woulldn't expect someone who isn't into classical music to recognize Gershwin's Rhapsody in Blue just by listening to it, I wouldn't expect someone who doesn't particularly care about a sport to know what teams play it or have more than the most rudimentary knowledge of the rules of the game.
There are so many things that, truly, are part of any given country's culture that it's just not reasonable to expect people to have more than an extremely superficial level of knowledge about them. People gravitate towards what interests them. They often forget things they have been taught (either in school or elsewhere) if it has no relevance to their lives.
Also, I live in a city that has no professional sports teams. I know what our minor league baseball team is called only because the baseball stadium is across the street from my apartment and I drive past it to get home. I don't personally follow sports because I don't care to. What I know about the rules of any game I learned in PE while I was in school, and I'm sure I don't remember all of it.