Inertia, or lack of real reason to upgrade. Personally I'm still on a CPU from 2013(Intel Core i5-4570S). Havent really felt the need to upgrade. And pretty happy that I went with 16GB ram back then, since its still enough for me today(browsing/light gaming/coding). I've probably spent 10 times what that CPU cost on SSDs since then, so its not a cost issue for me. And more recently a Geforce 1070 TI. I've been thinking about upgrading, but I really need to see significant IPC lift to bother. So maybe a Zen3 or Intel next-gen sometime in 2021. If they manage to raise IPC.