It seems the tradition of argyle hose for formal/evening only arose from the hose being expensive and thus very special. However, I do not think there is anything particularly formal about them and I wear them day and night. In a world where a single man might own three kilts, the idea of argyle hose being expensive seems kind of secondary. However, they do tend to be pricey, so take good care of yours!

Of course, this is just my own opinion- others may disagree entirely