Undoubtedly that's true, but the same applies to flying to most European destinations from Scotland but EZY nevertheless do operate many European routes from EDI and GLA.
Following GSMs demise, EZY had signed up to add an A320 at GLA back in spring, flying to the likes of the Canaries, but pulled out at the last minute and sent the aircraft to LGW when EI pulled most of their LGW ops. Although I believe GLA had and A320 swapped for one of its A319s over the summer peak, fares were still very high.
Despite one or two new routes at relatively low frequency, EZY haven't really added anything significant in Scotland for ages. Either they are not really interested or they have been caught out by the speed of FRs expansion, particularly at EDI and haven't been willing/able to respond.
Whilst it is obviously a case of business first and new routes must pay their way, it is a shame that the pax in Scotland, who gladly supported EZY when it was in its infancy on GLA-LTN in the 90s, are now being bypassed when it comes to expansion. FR clearly feel they can make money by expanding in Scotland, so why do EZY seemingly feel they can't?