I'm guessing you're running your windows account as "administrator" right? Everyone does.. it has the least restrictions to install apps/modify the core OS.. That is a right you have because it's your hardware.
What if Dell, HP.. Lenovo.. or any of the other big players out there locked you out from admin on your computer and made you run everything as a "User" account.. how long do you think those companies would be in business?
Yet this is EXACTLY what the cell phone manufacturers are doing every. single. day.
If you break your windows machine, you can easily re-install windows. Instead of cell phone manufacturers voiding warranties, they should simply provide the tools to reinstall the OS on an Android device.. It makes 0 sense why we continue let this crap happen.