Motorists and street furniture in bike lanes are not the only things helmets protect you from. Pedestrians, other cyclists, mechanical failure, rubbish in the road, oil patch, black ice; any number of things can result in you hitting the ground even when entirely separated from motor vehicles. Meanwhile, more and more people are using e-bikes and spending a larger proportion of their time on the bike doing 20-30mph or more.

Hitting concrete with your body at speed is not going to be great for you regardless of the exact cause or exact body part. Just wear the helmet, pity's sake. Why be a meat crayon?