I suspect Flybe aren't particularly popular in Cornwall. After a lot of hype about launching flights from Newquay this time last year, they've pulled out with as much speed as they came in:
Newquay-Southampton: Dropped before it started
Newquay-Geneva: Dropped before it started
Newquay-Birmingham: Dropped
Newquay-Glasgow: Dropped within a couple of months of starting
Newquay-Edinburgh: Dropped, for the winter at least
Newquay-Belfast: Only operated in the summer (and Jet2 are picking it up next summer)
At the same time, to be fair they have done good things at Exeter, especially with routes to Spain, Portugal etc which probably wouldn't work from NQY.
I'm sure ASW's route from LGW to NQY does ok, but they only have to fill 50 seats and they get half their load from PLH. I'm guessing that if Flybe have a Dash8-400 and some LGW slots going spare, they would find something far more lucrative to do with them than flying to NQY!