I think comics scholars have sometimes been bad at articulating why other academics should be interested in comics if they’re not already. This is more of a problem for comics studies than for other emerging fields, like games studies, because comics are still a fairly marginal medium, and it’s not always intuitively obvious that comics are worth studying simply by virtue of their cultural importance and visibility.
And I think one good argument for why comics are worth studying — and this is an argument that people are not really making — is because comics are a microcosm of many different sorts of problems related to media and materiality. If we look at, for example, the way comics are affected by transitions from print to digital culture, we can draw conclusions that are generalizable to other media. Christensen and Magnussen say in the prologue to Comics and Culture that “comics represent an almost complete catalogue of semiotic problems and were, in that respect, an appropriate subject of study for theoretical semiology.” I think you could similarly say that comics are a complete catalogue of media-theoretic problems and therefore an appropriate test case for media theory.