FASHION - Here is a fun fact... men in a relationship don't buy new underwear. Their wives or girlfriends do that for them most of the time.
It is difficult to estimate just often women buy men's underwear, but I would estimate it to be somewhere in the range of 90%.
Speaking for myself, I buy new underwear once a year... and I have big drawer fills with Dockers boxer briefs, boxer shorts of various types and so forth. I really probably should throw some out.
Eventually the elastics wear out and you have to throw some of them out anyway. It happens.
Some of them I can even tell you which ex-girlfriend bought them for me. Some of them Santa Claus and reindeer on them so that gives you an idea of what time of year they were given too.
When you consider quite a few men in North America are freeballing [walking around with no underwear at all] then you start to realize that men simply don't care that much about their underwear. But women care. Women care a lot evidently.
It all reminds of several clips from Seinfeld. For example the clip of Kramer below wearing Calvin Klein underwear. Does Kramer care what brand he is wearing? No. The guy is clueless. There is other clips of Kramer too walking around in just his underwear, and in one incident freeballing, but my point is made. Men just don't care.
Part of it I think is because the male body (on average) is NOT a work of art. True, male supermodels often market underwear, but its not the men they're marketing towards its the women who secretly wish their boyfriends or husbands looked like a male supermodel.
As a man who buys underwear once per year I will admit I go for quantity, preferably a brand that is also quality at the same time. Thus a brand which sells a 5-pack of underwear automatically gets ranked higher on my priority list.