I do it from time to time, if it's necessary. Usually when I'm away from the house - it would be disgusting to do it indoors.
See, I can't understand why it's disgusting to cleanly blow snot out a nostril onto the ground, but it's not disgusting to take a tissue, wipe it all over your upper lip - worse, if you have a mustache - and then PUT IT BACK in your pocket - gross! - so you can use it AGAIN.