A commenter sums him up:

I always thought he was a ‘coffee table’ version of the blues for watchers of ‘Later’ and readers of music magazines anyway. The people who liked it were fairly unlikely to be existing fans of blues. You could see then it was all aimed at that market, and that’s without even knowing there was any doubt about his purported background.

The indie world to which Seasick Steve was marketed was always more concerned with image over substance, and perfers to listen to “blues” ot “rock” or “folk” in much watered-down forms.  No wonder they loved Seasick Steve.