That is a helmet. It only works when it is strapped on. If you don't strap it you may as well not be wearing it because it will fly right off your head if you get hit.
The motorcycle crash I saw a couple days ago was tragic. An idiot with a reflective cover over his license plate slammed his car into a motorcycle. The motorcyclists helmet flew off his head. When he hit the pavement his skull cracked.
I saw cerebral fluid leak from his head and form a pink puddle on the asphalt. I saw his useless helmet up the road from his limp body.
Please, strap your helmet.
Please strap your helmet.