I blame a lack of good stories and little exposure
There really HASN'T been anything for Darkhawk fans to talk about... War of Kings was the last one I saw... but that was in 2009 and it's main point was 'Everything you knew before doesn't count!!!' Which means I never actually finished it. (can't stand the inhumans OR Shiar... so that was a hard sell anyway)
Ohhh and Avengers Arena... but he was background for most of it, and the amulet that few people could access... was handed around to everyone... >.<
I'm a bit curious what or If he'll show up like next in the All-New Marvel... O.o