The reason tolerances are more important today is that construction has become more sophisticated. Now we buy building components manufactured off site to normal factory production tolerances that are considered tight by traditional field construction standards. Formerly we built everything on site and made it fit. Another reason tolerances have become more important is that today's sophisticated owners know precisely how their buildings will be used and they have more demanding requirements.
Tolerances must be given greater attention during design, or problems will continue to arise and haunt the designer as well as the contractor and owner.