"Microsoft was hoping that users would grow tired of the limitations and purchase a key for the full suite"
case 1: people do not use Office at all.
case 2: others use so few of the features, the do not run into the limits.
case 3: some uninstall it completely, and switch to a free suite, LO for example.
case 4: some uninstall it, to use a former Office, like 2007 or 2003.
etc.
Running through all the cases, few will will remain in the end, who actually buy it.