1500m has been the ICAO "VFR" figure for countless years.
JAA made it 3000m for JAA licenses (unless accompanied by an IR or IMCR).
The funny thing is that VFR navigation, as taught, i.e. dead reckoning, won't really work in 3000m (unless you fly really low and slow) and won't work at all in 1500m, at plausible fixed wing speeds in unfamiliar territory
Not that I am complaining, as I use GPS...
It is also slightly perverse that an IMCR holder can fly VFR down to 1500m (and could for a long time) but to takeoff and land under IFR he needs 1800m
But the other day I flew a NP IAP with an MDH of 800ft, in what was VMC with a vis of apparently about 1500m, and only just got visual shortly after reaching the MDH and just before having to go around. It was a good illustration of how difficult flight in 1500m vis can be.