When my kid was a kid he was riding around on one of those little 50cc quads. They don’t go very fast, and he was just on flat, level, ground, so we didn’t bother putting a helmet on him. My friend and I were standing there watching him, and chit chatting. My son started getting more daring, and gassing it through figure 8’s and almost tipped the quad a couple times leaning the wrong way, so we decided that he should put a helmet on “just in case”. A couple minutes later he flipped the quad and broke the face guard of the helmet in half. That would have been his jaw, had he not been wearing the helmet. So yes, even when you’re going slow, and just diddling around on a quad, you should always wear your helmet.