Not sure why LCY itself would even care to be honest.
It makes absolutely no difference in ATC terms - more often than not the aircraft stays with radar nowadays...... the beauty of Class D VFR v IFR.
There may be other reasons - possibly noise?? It is certainly far busier than ever right now - and a couple of times this week there have been one waiting to get in or squeezing in against the other one on the ground.
As a mere ATCO, can you tell me exactly what HUMS is?