workaround, install ubuntu tweak, and enable the tweaks->miscellaneous->natural scrolling
Gnome already implemented this, now, each developer has to enable this function in his program. As you may know, each part of ubuntu is one single program, so each developer has to be agree to do this.
Why it is not implementable as a operating system functions?
Some applications manage the scrolling in his manner, so, if we activated the elastic scrolling for all, some applications will loose his possibility to scroll, and this is not acceptable.
I already talk with developers to do this, and I already do and idea in ubuntu brainstorm like this, but at the moment, this is not possible.
This idea is a duplicate from an idea of 2009, so, you can imagine that this is wanted since a lot of time.