Why is there always a need to upgrade?
The XP Kernel (Core operating system) was unable to be made any more secure, a new kernel was written, that became Vista, which was almost universally hated. They kept the almost the same kernel (some tweeks) and re-wrote it to Win 7, very much like XP and loved by many, but...
They missed the boat on tablet PC and smart Phones. They (they is Microsoft of course) wanted to get into that area and fight back against Google's Android operating system. Hence Win 8 was written to operate on devices as well as Laptops & PC's, but it was written for the small touch screen systems mainly, very poor OS on larger computers with Mice and keyboards etc.
So Win 8.1 arrived to try and please the Laptop/desktop users, hmmmm!
Now Win 10, a whole new kernel again. It's Free (their ain't any such thing as a free lunch) and a whole new way of doing things. They want to trap you into the MS environment (just like Apple have done to Apple users), preferred save method to MS Azure (their cloud system), of course you can buy more cloud storage. Only let you buy programs through their App Store, Continually want to sell you more capability for the bit of Win 10 that was free, or Office 365 (nearly as much per year to rent as it was to buy Office 2013, and, and, and... it all costs more.
Worse still, whenever you search for something that doesn't directly match a system setting or installed app, Cortana taps into Bing and brings up a list of web results by default, rather than scouring your local hard drive for relevant files. Conducting a local search requires an extra click of the My Stuff button in the search results. Do you like the idea of every search result you run going to Microsoft's servers just so they can direct better advertising at you?
For anyone that's interested in how to uninstall Windows 10 and go back to Windows 7 or 8 - follow this link
http://www.pcworld.com/article/2960692/windows/how-to-uninstall-windows-10-and-go-back-to-windows-7-or-8.html#tk.nl_pwr