Economically, why does it cost more to stream movies than to rent the physical DVDs

I was always told dvd tapes cd’s books and such that was rented/lent out ect cost more because your buying a license from clearing house to rent/lend it out

its why when your puppy chews up your library book you cant just buy a new one at Wal-Mart…

Even if there are higher costs to stream, why isn’t there any sort of price differential between services?

When I search for a movie on my Roku, it finds all the services that are offering it and their price. Recent movies are typically all the same price–about $6 for the HD rental. That’s across Google Play, Amazon, Vudu, and Fandango. Since the product is exactly the same no matter the provider, I would think the providers would compete based on cost, but they don’t. The times that there is a difference is on an older movie. So maybe Jaws is $2 on one service and $3 on another. But the new movies are all the same price.