Much angst around the provision of qualified persons in the Tower flows from the fact that, once licensed/certificated, the CAA have a say about what you can and can't do.
The requirement to have a licence/certificate for certain operations was removed years ago and recent changes brought about by SERA have further widened the scope to operate from an acceptable landing ground.
Not only Shoreham but any similar UK aerodrome has a choice. Each has to weigh pros and cons before deciding.
Some issues against include the loss of ATZ, loss of certain types of training and loss of flights requiring the use of a licensed/certificated aerodrome. A fascinating issue would be the status of an existing RNAV(GNSS) IAP notified having used CAP1122 for the safety case. As you all know, the tables in that hallow'd CAP include all types of places and ATS (or not).
So, cost savings from staff reductions (Licensing fees, ATC, RFFS & Ops Staff) versus loss of certain income, though offset by increases in other movements.
Not donning tin hat, not ducking behind railway embankment.