DOS is for awesome. I mainly use it for old games, tinkering with old hardware, etc. As a hobby I like collecting old parts and systems (not just PCs, game consoles as well), and for older machines, DOS is appropriate for the time as Win95 or later might be too new for them. There's also something much more tactile and satisfying about using the command line that's cooler than simply dragging and dropping stuff in Windows.
Plus there's also retro games, getting them to run on vintage hardware is awesome, and just getting them to work as they did 15-20+ years ago is fun. Plus, a 486 DOS box is really quite awesome since it'll run most DOS era games(on genuine period hardware), however there will be older games from the XT/286 era that run too fast on a 486 even with the Turbo button off(Stellar 7 comes to mind), and a slower machine is needed (which 386's work great for). Plus you can get into even more hardcore retro stuff like Monochrome and CGA/EGA graphics and monitors, the list goes on.
Stuff that drives the mind of the Retro Nerd.
= Phenom II X6 1090T(HD4850) =
= K7-550(V3-3000) =
= K6-2+ 500(V3-2000) =
= Pentium 75 Gold(Voodoo1) =
= Am486DX4-120(3DXpression+) =
= TI486DLC-40(T8900D) =
= i386sx-16+i387(T8900D) =