Windows does a fairly good job at managing memory. If you only had 4GB it would try to manage that by not running out and putting the rest of the load on your HDD slowing things down big time.
I had 16GB and when running some work programs it was in the 15GB area I have since added 16GB more for 32GB I can now render the same size file and it uses in the 23GB area and is much faster.
That is very normal the more you have the more it will use to a limited extent. (this is not saying if you added a ton of ram it would use a lot more as of now for gaming 16GB is about the sweat spot) A few years ago 8GB was fine and still is in most games but some of the newer games really like the extra memory. 10 years ago you could get by with 2/4GB of...