IMHO any met conditions in which one is going to actually get an SVFR clearance are actually perfectly flyable under VFR rules (clear of cloud, etc).
One might meet the vis rules but not having a horizon to work to one would be effectively instrument flying but hey this is legal VFR so let's not go down there
Is it surprising that ATC sometimes take a cynical view when a pilot states that they are VFR in marginal conditions?
That is another huge can of worms. How does ATC know what the pilot actually sees? Even in the "extremely obvious" case of "illegal VFR" of the airport being OVC003, you don't actually know that the pilot is not descending through a hole somewhere. This is why it is not ATC's job to police this, and IMHO this is as it should be. The ATCO would be in a very poor position to revoke some clearance on the basis of thinking he can see something the pilot cannot.
I believe there have been prosecutions in the USA for VFR flight into IMC, but these were (one hopes) departures into immediate solid IMC witnessed by others. Still, it is an iffy area. Not as iffy as doing somebody for flight into 'known icing'