England has a massive amount of professional clubs compared to other countries. There are 72 teams in the football league and literally hundreds (thousands?) of pro/semi-pro clubs around the country. I can understand why people may have a local team and still support a bigger PL/Championship club that they have an affinity with.
Wigan is a good example. It's a town in Greater Manchester that is traditionally a Rugby League town. Wigan FC up until 2005 weren't even in the PL; in fact, they were way down in divisions 3,4,5 etc until relatively recently. So if you're a kid growing up in Wigan, then sure, you might keep an eye on your local team, but you're naturally going to gravitate towards United or Liverpool who are in the top division, on TV every week, with massive followings and who are based just a few miles away.
It makes Wigan's current position and their FA Cup run even more remarkable.