Why having a sock made up on a 240 needles machine it is a better option compared to a lower numbers of needles machine ? The reason is in the knitting. First of all, of course, the finest yarn can be used on highest numbers or needles machine only, as the others have needles too big to "catch" it. Second an high numbers of needles ensure a finer knitting and this mean a more "flexible" and elastic knit, which hold the sock better to the leg without putting too much pressure on it. The fitting is a lot better and consequently the sock is more comfortable. Third one it is a fashion reason : with an higher number of needles the definition of the design is a lot better and you can realize smaller designs with better look. Last one : specially during Summer having a very fine sock is better for the transpiration of the skin and to keep your feet cooler.
On the picture cashmere/silk lady's overknee