This way it is possible to create workflows where you have small specialized apps that complement each other. You would open a file by dragging it to the first app, edit it, drag the result to a 2nd app do some more editing, then drag the result to the next app and so on and save only the final result back to disk. This is basically supporting the Unix philosophy of having many small programs that do one thing well, and combining them to achieve the desired result.
Instead what we now mostly have on all platforms are huge monolithic programs that try to cram every possible feature into a single package. One reason for this, is in my opinion, that a workflow that is similar to the RISC OS way of dragging from app to app is just to cumbersome on systems without drag and drop between apps, as every step one has to go through the filing system, saving a file by browsing through a directory tree and browse the directory tree again when loading the file in the next app.
I tend to use my iPad as my primary computer - and once you get your head around the fact that everything runs off the share menu it's basically the same concept, without the physical dragging.
This was 1988. TrueType for Mac was not until 1981, and it used quadratic Bezier curves, which are inferior to cubic, and AFAIR did not use anti-aliasing and the hinting system was inferior to that used by RISC OS.
I really wish Acorn had licensed their font technology to other companies, but like many other of their technologies (such as Econet and the video codec used by RISC OS) Acorn developed these for their own use only. It is almost a miracle that the ARM processor escaped the Acorn-only fate of so many other technologies.
http://rox.sourceforge.net/desktop/
It would partner really well with a distro such as GoboLinux or possibly even sta.li.
I guess you kind of have the same thing in mocOS with the proxy icon.