It doesn't help that BC has never been good enough, for long enough, for anyone in Boston to really care.
I grew up there, and believe me, when Doug Flutie was on his way to the Heisman in 1985, people really cared. But within a couple years of his graduation the program was terrible. Coughlin revived it, and Dan Henning (and gambling) ruined it again. O'Brien got them back, but they were never a top 10 team, and that's what it takes to cut through the pro sports clutter in Boston.
And a HUGE factor is that BC is a private school. In a city with a TON of private schools. There are more BU, Northeastern, Harvard, Tufts, Suffolk, MIT, etc. alums in Boston that are indifferent to/hate BC than there are BC grads.