Consumer chipsets have long supported USB, SATA, and PCIe using shared PHYs giving motherboard vendors some flexibility to decide which IO lanes they would like to wire up to SATA connectors vs USB connectors vs PCIe/M.2 connectors. (This worked great when all three were in the 5-6Gbps range.) Since SATA is now the slowest of those three interfaces, it doesn't really drive up the die cost much. It's pretty cheap for the chipset to continue to have a few SATA MACs on die, and giving the motherboard vendor the option to use the PHYs for USB or PCIe means there's no significant opportunity cost or inflation to the pin count to support SATA.

We've already seen the typical number of SATA ports on a consumer desktop motherboard drop from six to four or two. We'll probably go through a period where zero is common but four is still an option on some motherboards with the same silicon, before SATA gets removed from the silicon.