The textile industry was one of the big drivers of innovation. Apparel was made to fit every customer. Tailoring  became a well known profession, and goes back into history with methods passed down over generations. Standardization is based on the technological advances of garments. 
Let's keep in mind that corset & tailoring were all about shaping the body, distorting, often even harming it. 

          When tracing a garment, one can use Pattern drafting or Draping. 

Made to measure is essentially the same as draping. It is great for apparel with movements and flow, but can be challenging when trying to have consistency or standardization. 

          The dress form is a major element of draping, and has a very strong History itself. It's critical to note that the dress forms are already dressed in the undergarments (this is what their shape is based on, assuming the person  will wear undergarments). The posture/ Structure of the body shape is not “natural".
 

          To make some progress on that front, Alvanon created an extensive 3D library. Their bust forms are based on 3D scanned body types. Still wearing underwear, however.

One big challenge is the gap between thighs. We have soft tissue! It’s malleable. But you need gaps between limbs to work on draping... as a result, mannequins are never fully realistic.
Manufacturers have started to use different types of foam on mannequins: it’s a little bit squishier. Arguably, that gap in dummy "realistic" aspect doesn’t need to be covered because it then becomes cheaper to use a real person.

          Posture is also an issue. We don’t stand completely upright any more. We slouch, and are always looking down on technologic pieces, as such, the posture of the bust forms we use should be updated accordingly.

 

READY TO WEAR.

North American mens measurement chart is based on Military Uniforms from the 1800's: they were malnourished, different body type, different body tone… There is a chart with how RTW fits, compared to how people fit on spectrum, almost no one coincides. 

  

There can't be a worldwide standard in sizing:  Sizing, standards and pattern methodology vary from country to country depending on the population of these countries : both based on a different body type per population and a  different aesthetic. 

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STANDARD SIZE
ASTM “ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services.”

US dept. Of Agriculture - Bureau of Human Nutrition and Home Economics: Division of Textiles and Clothing (1941). 
The silhouette is incredibly hourglass, yet tiny. Feminine ideals vary extremely fast and often, it's hard to keep up with how a female body should look like. Dior influenced the ideal of women after the war to make them look weak and needing assistance again. 

1955 Voluntary standard. NIST 

Over the years, body types and stature have changed so much that looking at body types is necessary to function as a designer nowadays. To try to solve this problem, the CAESAR STUDY: a 18 to 65 - 3D anthropometry database has been started a few years back. All bodies are real world examples of people, scanned in consistent garment standards. It shows the differences in proportions and sizes. You can look up at all the body measurements of a 32DD for example. This dataset is extremely expensive (100,000. 00 USD +/-) but also incredibly valuable for the world of apparel design nowadays.