Garmin must have nearly as much money as GOD, if not why don't they team up with one major Heli /A/c manufacturer, the rest would soon be hammering on their door to get involved, seems odd to me or are there some gremlins not able to be ironed out of a system that acts as your eyes.
The Garmin systems with SVS are installed as basic equipment in the B407 and the AW119(I think) and will also be standard equipment in the B525 and B505. There are also STCs available for the G500 in the B407,206 and AS350 that I know of.
I would suggest that the issue lie not with the OEMs but with the regulators acceptance of the systems.