nope, don't wear one, literally only smacked my head one time on a bicycle and i hit the wrong brake and ended up needing a stitch because i landed head first in a nice plush lawn with one little rock right where my head struck the ground

i feel like i'm in serious danger if i'm at a velocity that exceeds my ability to break the fall... i had a fall a couple months ago on a steep concrete pavement and i did a pretty good roll as i hit the ground but it was bumpy concrete and i still have a bit of a ding in my knee... but my head didn't touch the ground

IMO, if you need a helmet you might be going too fast, and ok, sure, if you like going fast and don't mind breaking bones and shit sure, wear a helmet, but if you use it as transport and not an extreme sport then it's just stupid, probably also urban design plays a role here because some places just don't give any space for either bicycles or even pedestrians... sometimes it's kinda understandable, like here on the steep slopes of #madeira, very light traffic overall and very few people braving the slopes on a regular basis