No one is buying PS4's check its weekly sales. PS4 software is kind of doing what you would expect for a system which is discontinued in Japan for over a year. PS5 however has had weeks where 50k units of hardware is sold and no software in the top 30 selling over 1k. So that does in fact need explaining.
The Ps4 still has many releases in the last years, anyway:
The PS5 had games in the top 30 with still a low amount of HW sold
And so on..