The history of male underwear is unexpectedly short. Male underpants are mentioned in a trusted document first in the late 18th century. Undershirts are existing a few decades longer. Describing them as »sexy« would be a rude overstating. They were worn under the outerwear only and were hidden to extrinsic glances. Thus the shapes and colours were plain until boring. The term »passion killer« describes their erotic effect appropriately.
From the late 60th of the past century underwear slipped into the focus literally with enhancing sex education and shorter and shorter skirts. This development lead to a ballooning evolution of (mainly female) underwear. Male underwear is limited down to the present day into a couple of styles: The slip (brief), boxer and boxer brief, cycle shorts and the jock-strap.
The latter (with a protective hard inlay) originates from US highschool sport and will be worn over the normal underwear. Just in the gay scene it will be worn skintight (and butt enhancing).
Boxer shorts and its variations, tees and tanks are not only underwear and are widely accepted as streetwear in the western world. The market is spreaded into a couple of big brands, a lot of medium sized businesses and many local manufacturers which otter loads of different styles. Thereby synthetic fibres will be supplemented by cotton, bamboo and other natural fibres. Even fine rib is available again and behold: its chic!