On the contrary, in NetHack a towel is quite useful and is usually preferred over the blindfold. A blindfold can only be used to blind yourself, but a towel can be used to:

  • blind yourself (see telepathy for why you would want to)
  • clean the grease (from your can of grease) off of your hands
  • wipe cream pie residue off of your face (often desirable after an encounter with the Keystone Kops)
  • Rub out the writing in the dust ('engrave' with it to get this effect)

Aside from that, you should always know where your towel is. Ask hoopy_frood for more information.