In most cases logging in as ‘sa’ is not required for Dynamics GP. The exceptions are really installing/upgrading products and possibly troubleshooting a specific issue. The Professional Services Tools no longer require ‘sa’. Third party applications should not be requiring ‘sa’ either.
The point is that using ‘sa’ should be a rare exception, not the norm. Admittedly, ‘sa’ is incredibly convenient sometimes. So is parking in a fire lane. That doesn’t mean that it’s a good idea.