Marketing (ha ha)
Ever since the days when I had a publisher, I've been responsible for marketing/ promotion of my own books. That's how it is for everyone.
Since Twitter/X's decline began, I've sold fewer and fewer books. Facebook has never sold many copies of anything for me.
I am unwilling to pay Amazon to advertise to achieve the square root of SFA(I've done it in the past with spectacularly unimpressive results).
(If one of us succeeds, we all succeed).