Will Amazon prime become a necessity for music purchases..?

So... I have used Amazon for all our music purchases over the past few years, for a couple of reasons:
Autorip - Call me old fashioned, but we have a CD player in the car & we don't download music, just keep it on Amazon cloud player, so we can play it in the house using wifi, as not massive memory on iPad or phones, so it's perfect to pay for cd & get MP3 version for free.
Cloud player - it's all in one place. When you don't download the music, it's a pain having some on iTunes & some on Amazon or wherever.
Old music - all old albums now eligible for autorip, which I've bought on cd from Amazon in the past are on there, which is a fair amount of music.

This has always worked fine up until now. I've never paid for prime, because I normally just wait until I have £20 worth of stuff to order, so don't pay for delivery anyway & we only listen to the things we buy and don't stream other stuff. Recently however, I've noticed that some albums are not available to buy, unless you have prime membership. This baffled me, as I understand that they might offer discounts to prime members, but I can't see why they would refuse to sell items to everyone?
The first one I came across was Amber run - 5am. A fairly obscure title, so I thought, oh well, maybe they've got a special deal, because they are an up & coming band. Then however, I preordered Van Morrisons new album. We listened to it once on the day of release, but then I realised that I'd somehow used my company credit card when I paid (it's saved on my account, as I sometimes buy stuff for work) so I quickly cancelled the order, and went to replace it, ordering exactly the same items, but now Van Morrisons album is only available to prime members!
You can still pay to download it, but not buy the cd. I rang Amazon to query it, and they said that the status was changed to prime only yesterday.

I can't quite understand the reasoning, is it to force people to become prime members..? If so, will it spread to more and more titles..? I don't like being forced in to things, so now I am trying to decide what to do - abandon Amazon for iTunes, which would mean having our music library split over two locations, or bite the bullet & commit to paying for prime, for the pleasure of being able to buy the music I want..?
Has anyone else come across this, and what are your thought..?