What is the difference if a book goes to no-copyright ? It barely does not affect the price - every dealer still want it's cut and you are stuck to your digita

What is the difference if a book goes to no-copyright ? It barely does not affect the price - every dealer still want it's cut and you are stuck to your digital platform provider anyway..so pay up. And individuals can refer to the books anyway..so what's th point? Art I understand, it's easy to copy photo or painting and put up a webshop selling a mug with photo of the painting on it.. but again if it's 100 year old painting..isn't there ANY other picture for your cup that is better ?