Some types of skateboarding absolutely need helmets.
When you are going at the speed most of us go while street skating, park skating, or mini ramp, you usually slip out or trip.
Usually we land on knees, ass, elbows or hands free vast majority of the time. We hit our noggin very rarely.
But at vert or downhill bomb speeds, it’s a completely different game. You can go from standing to bodied before you know it. That’s why most very skaters and downhill guys wear helmets.
Sure, there may be a few guys good who are good and/or cocky enough in both areas that down wear helmets, but it’s a rarity for a reason.
Older guys in both scenes can tell you about how much head trauma they’ve seen or experienced.