One touch scanning is limited to 10 intentionally and as far as I know applies to every printer.
If you have 50 people listed as onetouch scans it clutters the home screen, which makes it take longer to populate, and the convenience is entirely lost if the user needs to scroll down 4 pages to find their name, at that point it is better to use Workflow scanning for most users, and Onetouch scanning for the select few who actually use it all the time.
If the Office is big enough people tend to use Scan to Home so they don't even need to find a template, just login and scan.
It is the same reason for email you can't set everyone in the adressbook as a favorite.