That's a casual viewer. I think you'd have to define "casual fan" as someone who at least knows the basic rules, and remembers the names of a few top fighters for more than 2 weeks after a major bout. - but they also probably would never purchase a PPV bout, nor would they watch any bout at a lower weight than welter, unless HBO-time promoted the snot out of it.
i dont think there is anything wrong with being a 'casual fan' as long as he or she is enjoying what they are watching.
Some of those guys aren't worth watching based on their carefully selected opponents and people that duck them. Paul Williiams will always have high out put fights. Sergio is just a monster.... that's why he and Paul Williams will always be forever linked. Andre Berto... got scared of and old Shane Moseley. Mf went to Haiti for the first time ever to back out of a fight.
How do you know who contribute to the gates or the PPV? the casual fans or the hardcore fans. Then maybe the distinction will be more important.