Amazon and Kobo provide apps to let you read their ebooks on iOS, Windows, Android and MacOS.
apple lets you read...on Apple. And even MacOS is recent.
everybody can spend their money however they want but I'm not going to pay money for software, or do screenshot workarounds, just to accomodate their agenda when I can instead use my money to buy books from someone who tries to accomodate me.
I'm the customer: so you cater to me, I don't cater to you.