I think the problem lies in that prices for bespoke garments are way too high.
Here in Switzerland, you can have still a bespoke suit made but there are very few tailors and they would charge areound $4000 for a suit.
Let's correlate that with the working class salaries.
If you consider that an standard clerk here earns around $4000 per month and a professional or middle manager would be around $7000 per month, this is a comparately high price to pay... even in this country when salaries are higher than in the European Union.
Let's compare this to the situation I have seen in Peru. I had bespoke suits made when I was travelling there, priced around $100-$150 depending on your choice of fabrics.
If you consider that a clerk there would earn around $300 per month and a middle manager or profesional around $1000, then the ratio is much more acceptable for a failure.
A friend of mine that works in a bank in Peru, receives every year a tailor-made suit as a uniform. So the bank contracts a group of tailors to build suits for all employees, regardless of their rank. so everybody has a tailor-made suit.
Even if $100 is considerable for a profesional that earns $1000, it is something you can take a risk about, and this also makes that more people get their suits done by tailors and consequently there are many more tailors for taking the work.
Sure, the quality level is not the one you expect in Britain or NYC. But certainly the suits made there are not 40 times worse.
If we correlate this to Switzerland, average working class salaries, a tailor-made suit could cost $700 which is a fair price and certainly many people would go for it over RTW, and this could revitalize that activity.