The point of inspection to ensure the part meets specification and the point of specification to ensure the part works in the target assembly or application. Parts that are inadequately specified and inspected may simply not work, thus wasted money and time.
The facts are that the GD&T standards used in industry are the ONLY dimensioning and tolerancing standard we have. Seriously, keep in mind that the GD&T standard includes limit type dimensioning.
#1 - minimal if not free
#2 - 99.9999% of the time - Cheaper than a non-function part making it to assembly minimal with proper equipment (1 Ė minutes max for very-very complicated part).
#3 - Free, with the proper inspection equipment.
The most significant problem Iíve seen in hundreds of companies Iíve trained at and reviewed their engineering drawings all across the world is over specification of tolerances and or placing nonsense on the drawings. This is not a GD&T problem but a designer or engineer that does not know what the functional requirements are or the target manufacturing process capabilities is as well as just not being knowledgeable in proper design.
See the following for more information