for someone who is new to it, I'd tell them wear the mask, period, I don't mind my risks in life, but curiosity can cause blindness, you are working with the closest thing to the sun available at home when you are welding, and you shouldn't do anything close to staring at it, if you are new and learning where the wire goes, you need to be able to see what you are doing or it will look like pooh at minimum or you will weld something you can't afford to replace...
that said...I TACK without a mask all the time, I agree no one should weld continuously without a mask, (have several flip downs since there seems to be an audience and help around alot)to be fair I do wear safety rated sunglasses and turn my head with my eyes closed when I tack, which isn't enough for welding, but it is enough to do 2-3 seconds of tacking IMO. its not a "looking bad" thing, its a mix of laziness and being hurried to get as much as I can done when I can get to work on it.