Why people call Boston the Hub?

Because it thinks of itself as the political, economical, and cultural center of Massachusetts, if not New England. Also, when you look at a map, the highways look a little bit like a wheel and spokes, with Boston in the middle.

What Boston is: The Hub of the Universe. First coined by writer Oliver Wendell Holmes, who actually referred to the State House as the hub of the solar system; today, a plaque in the sidewalk in front of Filene’s downtown commemorates the exact center of the universe (although they’ve mostly covered it over now with some sort of storage area). Actually, pretty much the only people who use the word anymore are headline writers looking for a short synonym for “Boston”

Just so long as you don’t call it “Bean-Town”.