A tight sole stitch is not something that necessarily makes the shoe better from a purely qualitative point of view, but a very sparse ones looks quite dull, and a very tight hand-sewn one such as the one in the picture is impressive craftsmanship.
The shoes are made by the Japanese bespoke shoemaker Eiji Murata, aka Main d’Or, and the stitch density is 16 spi (stitches per inch). Usually when one make a sole stitch by hand it’s made between 6-10 spi, sometimes 12 spi. Higher than that is rare today. However, for Eiji Murata, the standard is 14 or 16 spi (he makes 18 spi as well, as you can see in this report, but he says that it’s not very practical).