For example, measurement is not as easy as "wrap a tape around your arm". You have to take multiples to make sure you get people as they add water weight, you have to take it at the right spot which might change for each person, etc etc. Then, machine sewing still isn't as good as hand sewing. If each pattern is different then it's difficult to automate the sewing. Lots of little changes in each suit make it tough to both automate and maintain high quality.
I think the bigger question is how to automate the sewing. If we could do that, I imagine it would make it much more scalable.
I have a friend who orders custom clothes from China. The quality is quite high and the price is lower than non-custom clothes for sale at Nordstrom's. Who is going to spent money making a machine to do this when the human labor doesn't cost anything?
When you get a bespoke suit made, you walk in and sit down with consultant and you figure out every little detail. He helps you pick a pattern that matches your coloring, label width that matches your body size, number of buttons that match your personality. You end up with a suit that is 100% unique to you.
I'll bite: what correlation is there between your personality and the number of buttons on your ideal suit?
Single buttons have their roots in the single-breasted dinner jacket or tuxedo. If you want your jacket to have an increased level of formality, you'd go with a single button.
Two-button suits are more standard, common for business and every-day suiting. Formal enough for the majority of situations when you'd wear a suit, but not quite "after six" level of formality for an evening event or dinner.
Three-button jackets should be left to casual suits or odd-jackets. Adding more buttons on the single-breasted suit adds an increased level of informality. Works best on casual, seasonal fabrics like seersucker, linen, tweed, corduroy, etc.
Double-breasted jackets have their roots in the military and are often paired with peak lapels, which are more formal than the notched lapels of most suits. So, a double-breasted suit would be definitely on the more formal end.
So, I wouldn't say that buttons are about "personality" as much as it is the situation in which you'll be wearing the suit.
What's unique about bespoke is that the tailor (technically, the cutter) will make a brand new pattern just for your body, which will be based on a much greater number of measurements. Also, the fitting of a bespoke suit involves multiple fittings (http://www.thesimplyrefined.com/wp-content/uploads/2012/02/B...), using each iteration to ensure a perfect "fit" in accordance with the tailor's vision.
Made to measure suits, on the other hand, involve a single fitting. After the fitting, the suit is made, and can only be altered to the same extent as, say, a standard size suit that you bought at a store.