<p>It is what is commonly called “made-to-measure”. For men whose build* fits poorly in off-the-rack suits, this can be a good option that is not extremely expensive. Of course, one has to compare the quality and other characteristics of the suit, as made-to-measure" is intended mainly to get a better fit. Note that there are also “bespoke” suits, which are usually more expensive and offer a higher degree of control and customization by the customer.</p>
<p>A man who would find choosing made-to-measure suits over off-the-rack suits useful in terms of fit would likely also find choosing made-to-measure dress shirts to be better fitting.</p>
<p>*Mainly, it is athletically built men who have a lot of trouble. Suits and dress shirts in the US are nominally designed for a “drop” (chest minus waist) of 6 inches (there are off-the-rack “athletic fit” suits of 8 inch drop and “portly fit” suits of 4 inch drop, but those are rare). Athletically built men may have a drop of 10 inches or more, which may be difficult to alter an off-the-rack suit to and still look good (more than 2 inch alteration is less likely to work well).</p>