These kind of points have all been raised before, STN included. Whilst there is now an option, at STN, to by-pass the yellow brick road of duty free shopping (for a fee of course), it all boils down to revenue, and will especially do so now going forward more than ever I'm sure!
People loiteirng at gates watching planes are not spending money in the departure lounge. There is the capacity argument, but that can be adapted by displaying the gate a bit earlier when neccessary. Putting a "Go to X gates" on the board may just move the problem elsewhere. I know this is done at LHR, but frankly they don't have such a big terminal capacity issue (just runway) and the fact their airlines are willing to pay more for better facilities makes the passenger spend not quite as high a priority.