In the desktop world, "pure" G-Sync monitors tend to cost more due to the direct cost of the G-Sync compatible display controller, and I assume there's also some indirect cost in there to properly certify these as well as in-house R&D and test. In other words, there's an extra cost that's inherent with introducing G-Sync into hardware. On the flip side, G-Sync Compatible does not require extra hardware as it leverages functionality in existing specifications to handle variable refresh rates. Although, I do recall seeing a video showing that Nvidia still has to test your monitor for it to be rated G-Sync Compatible. I think that's why there was that hubbub over some Samsung TVs that could be setup in the Nvidia drivers as G-Sync Compatible even though Nvidia did not certify nor list them as such.
So, in regard to laptops, there are "pure" G-Sync laptops out there, but the problem is that they tend to be priced closer to the $2000 mark. So, maybe the better question is... why don't we get laptops that support VRR? Now, it's worth noting that G-Sync -- while being more limited -- is arguably better than VRR. VRR's major limitation is that it's only active within a specific framerate range. For example, LG's CX series OLED monitors support from 40-120Hz. Although, if you're working with a 60Hz screen, you'd be limited to 40-60Hz.
