One (but certainly not the only) reason is that Apple rarely discounts their products and even if they do it’s not by that much.
It’s not that hard to find a high-end/$2000+ PC laptop for 40% or so off 1-2 years after its release, not so much a macbook. Apple is still selling refurbished M1 airs for $849.00 from 2020 ($999 was the price on introduction)