Only the NUC7i5BNKP and NUC7i5BNKQ models came with memory and storage and Windows 10 preinstalled. The base NUC7i5BNK model is a kit and required that memory and storage and Windows 10 be separate procured and installed.
On Amazon, I was looking around for a complete NUC Kit (storage + memory + mouse + keyboard + monitor) - I don't see one on Amazon.
Amazon sells many of the Intel NUC models configured with memory and storage, and some models come configured with Ubunto or Windows operating systems.
To n.scott.pearson's point - most of the NUC Kits do not come configured with memory and storage from Intel. Personally I like this because I can spec the NUC Kits to my standards without feeling I've had to compromise based on a re-seller's stock components.
If you want everything (NUC, memory, storage, OS), just search for one. I just participated in such a purchase from Amazon, and it went extremely well. Plugged in the mouse, and keyboard, and booted the nuc. Immediate gratification as W10 came up immediately. If amazon does not have what you want, there are other vendors.
If you want to build your own, which I have also done, find the kit you want, buy the memory and storage you want, get a windows 10 license, and put it all together.
Your choices are:
Intel sells the NUC products (systems, kits and boards) through the distributor channels. They thus have no control over or even knowledge of who will have them in stock. You will have to find a distributor or storefront with stock on your own.
Hope this helps,