They have lifetime payment options and end-to-end encryption features: Some alternatives to Amazon Drive that behave like a hard drive in the cloud are pCloud and IceDrive. It's probably very hard to market to this target audience effectively when so many people are familiar with DropBox and OneDrive that are often bundled with or supported by other services. I'm surprised they are dropping it given how big they are in cloud services but I could see how not many people would have found it to see the benefit of using it as an online-only drive.

Amazon Drive allows just dropping files into the space without syncing. A lot of cloud drives like OneDrive and DropBox keep files both locally and in the cloud and getting them to behave as online-only isn't all that intuitive.

I found it randomly trying to find a cloud storage provider that behaved more like a cloud hard drive than a synced drive. Review sites of cloud storage don't mention it often, if at all. I was going to say the same, I think they didn't market it very well. Honestly, I didn't even known that Amazon Drive was a thing, so maybe that was part of the problem. I think the market can only handle so many 'Drive' providers, but I am surprised that Amazon is tossing in the towel.

Amazon drive desktop app review