Literature is about as unnecessarily necessarily as tableware or ironed shirts.
A loss of tableware and an un-ironed shirt will not kill you. And the same goes for a lack of literature.
Literature, like tableware and ironed shirts, is an add-on. You can eat with your hands, sure; you can wear un-ironed shirts, sure; and you can surely choose not to read; but once you have the bare necessities, once you have the table and the shirt and the ability to read, in some way you’re just degrading yourself when you choose to mishandle these add-ons. It’s like throwing the cherry-on-top away because the ice-cream is enough.
In some weird way, it’s all unnecessary until it’s necessary.