Why do subscription movie services (Netflix, Amazon etc.) have a limited selection compared to subscription music services?

I have a subscription to Google Play Music All Access for $7.99 a month, and I can listen to just about any artist/album I can think of, unless it's really obscure. There are other similar subscription music services like this for around the same price, and they also get new releases and are only growing in selection (their licenses never expire as far as I know).

However, I also have a subscription for Netflix Instant and Amazon Prime, and their movie selection is much more limited in comparison. On top of that they don't get movies on the same day as DVD/Blu-Ray release, and movies are only on there for a short period of time before they expire. It's basically the movie channel of the internet.

If I can't find the movie I want to watch on either of these services I'll usually just rent something on Amazon, and I probably rent about two movies a month online maybe more (usually new releases). If it's a pricing issue, I would be willing to pay $30-40 a month for a subscription movie service if even 9 times out of 10 I could search for a movie and it would be on there.

Is there any reason a service like this isn't feasible, or is it just that the studios are stingy with licensing to streaming services?