The problem with keeping game installers is that the games take up twice the space. This doesn't happen with Steam due to its architecture. Basically: Games must be packaged according to Steam's specifications which means developers don't have the option to dump massive install package/archives on people's drives as well as the installed game. This has so many advantages: (i) Libraries are so portable that you can put your games on a separate drive, and they will still be playable without having to reinstall them even if you format your C: drive and reinstall Windows. (ii) Games are much more straightforward for the client to backup/restore because they conform to Steam's unique installation spec. (iii) If a game file becomes corrupt, the Steam platform can detect it (using the verify integrity option) and will download only that file. The client is 'aware' - if you like.

By contrast: (i) Game libraries on Origin are not portable and won't be playable - even if installed on a separate disk - after a format of C: and Windows re-installation because the installers typically make so many changes to the Windows registry. You need to run the installer again for every single one. (ii) Games cannot be backed-up/restored like they can on Steam because the Origin client is 'unaware' of the files installed. (iii) For the same reason: All games on Origin need to be re-downloaded and re-installed in their entirety if a single file becomes corrupt.

These are significant issues which make Steam a better platform for gamers in my opinion - despite all the other issues with the Steam client. I suspect EA will never be able to make Origin the same due to lack of foresight when originally building the platform. To make Origin 'aware' enough of installed files and registries changes in order to enable these features, they would have to design a new installation spec. and rebuild the installation packages of every single game available on Origin.