I'd disagree slightly. MAN doesn't have that much to offer sight seeing wise (I'm talking castles, Houses of Parliament, world renowned statues etc) but what it lacks in that it makes up in culture and general vibe. Therefore, IMO it lends itself very much to the repeat traveller. You'd also be surprised at the inbound sectors on Fridays from places such as AMS, HAM, CPH etc.... And not just football fans either. Indeed, Central Manchester in general is alive with the sound of trolley bags on a Sunday afternoon as people head home.
That said though, MAN has always been heavily skewed towards the outbound market and a surprisingly affluent one at that..... Those business and first seats aren't all being filled by business bods. Basilbrush is spot on when he says that we should never forget our bread and butter. IMO this should extend to when carriers launch "yet another route to the med" moaners.