94% of all programs won't run properly without those rights.
Unfortunately for the longest time developers for Windows got away with not giving half a shit about security. To make matters worse, when MS finally decided to tighten the screws, they went overboard by a long shot. You cannot even install a simple program without elevated rights.
And to make matters worse, "elevated" means "full access, anywhere". There is no granularity, it's only "can't do jack shit" or "total control". You cannot open up the program files to install a normal program without also giving that program the ability to drop a low level driver into your system.
Then again, if that worked, a lot of people would probably notice just WHAT kind of crap their beloved games barf into the deeper intestines of their computers for the sake of the all holy DRM.