>I have to carry around a helmet- yes I find this burdensome.
Unfortunately, I don't have the luxury of biking to work yet, but if I did, I'd be using a backpack for what I hope are obvious reasons. Any good backpack these days designed for cycling has a clip on it that attaches to your helmet so you don't have to carry it around. I even did this years ago in college when I biked to class; it wasn't a burden at all.
>And you accept that wearing gloves is ok, but you don't wear a jacket- so you know you may fall, and possibly scrape along the ground a bit, but you don't wear a jacket that most motorcyclists consider to be basic standard gear.
Jackets are incredibly hot. Bicycles don't go fast enough to mitigate this. Some skin scrapes are preferable to getting heatstroke.
>but my years of riding have given me intuition (in other words, my developed common sense) that the head is highly unlikely to be injured
The problem is, if your head is injured, it's either game-over or you suffer mental problems for the rest of your life. Other bodily injuries you can usually heal from. A broken leg? It sucks, but it heals. Skin scrapes? Not a big deal usually (not at bicycling speeds). Worst case you get a skin graft but that's not normal for cycling. But a concussion can leave permanent damage; the brain doesn't heal the way the rest of your body does. To make a computer analogy, I feel like you're talking about the relative risks to various computer parts, and equating potential damage to your laptop's screen to its hard drive. The screen isn't important, nor is the rest of the laptop: you can replace them at any time. But the hard drive is unreplaceable (going back to the last backup, which unfortunately we don't have for brains yet): if anything happens to the hard drive at all, you lose all your data and all your work, and you can't replace that.