Loading applications along with varying types of virtual management, shadowing or paging, dedicate the RAM requirements.

Your comment...

"Our OS Files don't grow, so the need for more Ram stays the same?" Not quit right in your thought...but close.

As you create data or user files, the manner in which our OS tracks them does not grow, with that, they do not require RAM resource to do so.

It's all about the manner utilized to track user data and that over head to a system. Sets of system files are created for this purpose(formally FAT). This tracking is managed on a virtual basis moving them in an out of RAM when an up date or creation is to be made. For FAT the whole file is loaded or shadowed. When they're in RAM they're in a virtual state until they are re written back to the permanent storage.

As you create data, the system meta data files grow(MSFT) , or, inode pointer lists grow(UNIX).

For a desk top PC this is not a problem ...as they are plugged into unlimited power resource.

For battery powered devices virtual management is a drain on power resource, as well as the type RAM normally utilized to preform the service, it requires refresh and power.

e.Digitals management is physical through the OS, they do not utilize a virtual scheme.

doni