Windows Vista and newer use what is call MAL (mandatory access labels) these are LOW, MED and HIGH. Low is a special very low access and is generally, at this time, only used by IE and Edge (what is called Protected mode) and they only directories with a Low labels are the LocalLow directory in each users profile. Medium is what standard users have access to and High requires either explicitly granted rights or a special administrator user token.
Background on "Run As Administrator"
All users whether they have admin rights or not run as standard users. When you get the UAC prompt, such as by select "Run As Administrator" the given process runs with a special administrator user token which has the required access to access a HIGH labeled resource. The way around that is to grant appropriate rights. Program Files and Program Files (x86) are both marked as HIGH label which is one reason you need admin rights to install software.