Interestingly whilst GLA's recovery post Covid has been slower than at EDI, I know of many people over here in the west who will catch flights from Edinburgh regularly. Since transport to and from Glasgow Airport is mainly quite poor, off peak certainly if you are in the South or East of the City, it is not significantly greater travel time to Edinburgh Airport than Glasgow (in the context of a long haul flight).
Ultimately those kind of airports only work either on direct short haul (i.e. Sun Holiday locations or European City Breaks) or Hub feeding - either LHR or AMS, or indeed the Emirates into DXB.
I don't think point to point particularly works outside major hub airports, particularly on Long Haul, and I suspect a good portion of pax to any of the destinations I've mentioned are transiting, rather than visiting those cities in of themselves.