I guess its the constant rights and royalty issues thats driving the agenda. Their competitors are doing the same. Like everyone else, Amazon is the issue for them as the latter has deep pockets and not pushed to make profits in emerging segments.
Yes - treating streaming releases like release on DVD or Blu-Ray would be better for us as consumers (availability throughout a particular market on one day onwards) but the film industry has never particularly worried about what's good for the people watching
We have both services (for what my opinion is worth, we watch more Netflix currently). We ended up with Prime when Ian Amazon bought Lovefilm. It's ok, but I'd like to see streaming on Android tablets/'phones that weren't the "Fire" branded ones. I'd also like the multiple watchlist idea from the postal Lovefilm service brought over to streaming.
Netflix has multiple lists (up to 5 "profiles" - for us, that's one per family member, and one for upcoming films the film review podcast i listen to is about to cover) and autoplay of the next episode in a series (you have to select and play on Prime - not too much of a hassle, but like most point and click interfaces, it's a pain with a TV or Wii remote).
If you're setting up Prime streaming elsewhere, you have to give junior your Amazon account password too. (Which is mad - there should be an option for a separate streaming password. Whilst Netflix doesn't have individual passwords for the profiles (it should) it doesn't have the worlds largest online shopping centre accessible from the single account everyone in the house needs to use it either). So for our use case, Netflix is the better experience - if you only need one list/profile, or have Kindle Fires for tablets, that equation changes.
I think that there's difference enough in the services to justify both, but then our only other TV service is freeview. I might think differently if I had a movie service too (although things that aren't on streaming, I tend to get on Lovefilm by Post).
EDIT - I also get the feeling that a lot of Season 1s are free on Prime, whilst following seasons are chargeable. I don't hate Prime, but if I had to choose between it and Netflix, I'd go Netflix as things stand.