The GTX 1650 and 1660 (and the variations thereof) were positioned at a lower bracket than the raytracing-capable 2000 series, and numbered in a way to capitalize on the prior positive associations with the GTX 650 and 660 series. Creating higher-end GTX parts without raytracing would go against Nvidia's long term goal of shoring up raytracing as a distinguishing premium feature, and would create a lot of confusion in the marketplace. A 1670, for example, would butt up against the RTX 2060 cards in pricing and possibly be faster while not offering raytracing, and would create a lot of angry confusion among people who paid good money for video cards.
edit: Nvidia ran into this issue to some extent with the FX series many years ago. For a little while you could buy an FX 5200 Ultra that had faster memory than an FX 5600, but ended up being a near-stalemate in performance because the 5200 chip had limited to no bandwidth-saving tech and cost nearly as much as the 5600 to make. It was a deservedly short-lived part that added to the swirling chaos of Nvidia's worst overall product line ever.