We have to remember that while Luton can be attractive to low cost airlines it would be less attractive to mainstream airlines. Despite the redevelopment Luton will still have no piers, no proper sized gate lounges, no CTA railway station and only one limited sized shared executive lounge. The jury is still out whether the short term car park actually gets a proper total rebuild or just another gravel patch job.
All this things and much more can affect customer and airline perceptions.