because SVFR is a dispensation to operate in conditions that should otherwise require compliance with IFR.
You may be getting close there but today the Stansted ATIS, for example, was specifically saying the "UK FIR is closed to IFR and SVFR traffic". However the weather conditions at Stansted today did not require SVFR.
London (Heathrow) were turning away lots of SVFR requests, including police helos, (unless Cat A) and a cheeky pilot in a Cessan 172 asking for a cross country clearance via the Heathrow overhead at 1500 feet!
So can anyone explain why VFR is allowed but not SVFR?
UV