a bit unrelated but I am confused why library's ebook has a waiting period? I am guessing it is a licensing issue, like how many copies the library bought and a

a bit unrelated but I am confused why library's ebook has a waiting period? I am guessing it is a licensing issue, like how many copies the library bought and are allowed to lend out? I hoped all libraries' ebook are unlimited. Is there an option for libraries to get unlimited copies of ebook from publishers? Is it just too expensive? Also, the amount of time you can loan a book is also an deciding factor. I noticed openlibrary's lending period is in 1 hour, vs. most other libraries lend out ebook for 3 weeks. The shorter the loan period, the more on-demand it will feel. I may borrow a book for three weeks, but I will only read it for a few hours during these three weeks, so most of the time is wasted. If the moment I close the library app, the book is returned, then everyone's waiting time can be shorten to almost 0. Why don't all libraries do that?