Why don't I see the newer phones in the Lineage OS list?

I’m starting to see not as many newer mobiles in the Lineage OS list as I used to. The US is a lost cause with companies not allowing their bootloader to be unlocked, but even the Chinese companies like OPPO, Vivo, OnePlus etc don’t seem to have their recent devices on the Lineage OS supported list. Am I imagining this, or...