If you are in the US, check out Hoopla digital for quite a few good audio books you can borrow. Bonus: you’ve already paid for it through your local library.
I suspect it has something to do with licensing, but I don't know for sure.
You may want to live in a world where a publisher sells a twenty Euro book exactly once, but that's not sustainable.
If you want more concurrent users, pay for it. The library has decided which level of concurrent users to buy.