It seems to me like you're being a bit hyperbolic in regards to how much the risk is increased when someone uses headphones or listens to music. If a hiker is listening to music or not it's your responsibility as a rider to be aware of them and to yield to them. If you're hauling ass on a multi-use trail and don't have a good sight line and you're surprised by a hiker that's riders error for going faster than they can safely react to an unknown obstacle, not a hiker who is wearing headphones. On the other hand if you're passing someone on the trail and they can't hear you because they have headphones on and they're surprised when you go by them again it's your responsibility on the trail to make sure they acknowledge you before you haul ass by them. There are plenty of hikers that wear headphones on my multi-use trails and I don't "almost hit" any of them. I'm not sure if the hikers in your area are worse than my area or if there's some rider error coming into play.I've almost hit numerous people with head phones on. After 20 years of climbing rock and ice fear has never kept me at home either. Riding up a fire road or similar with headphones on is one thing, but in general on a trail - especially a multi use trail one should refrain and be more conscious of what's going on around them. For everyone's safety. I have a helmet on and a 40# bike they're more likely to get hurt than I am.
I'm thinking of others more than my own safety.
As far a riders wearing headphones, most of us are more than capable of being aware of what's going on around us than you seem to be giving us credit for. Whether I'm listening to music or not I'm constantly scanning the trail picking my lines, adjusting my body position, jibbing, and playing. The fact that I can't hear someone down the trail is irrelevant because likely they're not making enough noise down the trail for me to notice that before I see them.
I understand that you appreciate not listening to music because you feel focused and you enjoy riding more. I think the problem is when you make the logical fallacy that if you're more focused while not listening to music that other people who are listening to music are less focused or significantly unaware of their surroundings.So potentially making it more unsafe by not paying full attention to what's going on around us, is good?
You'd be amazed just how much of the world doesn't have to worry about stuff like that.
We don't have much in the way of shotgun-carrying hillbillies telling us that we've sure got a purdy mouth and that they're going to make us squeal like a piggy, either.
No idea where you're going with that: not listening to music has the exact opposite effect to stopping me from enjoying riding...
There are a few things that I could be distracted from when wearing headphones such as signs of a mechanical failure, or a nuanced sounds of my tire breaking traction. Being able to hear that could mean that I'm riding more safely. Also not hitting gap jumps or doing large drops would be safer. I assess the risk to reward and make a judgement call. I think that risk is so marginal that it isn't a concern most of the time. I choose to listen to music on a chill ride. Not when I'm pushing my limit bombing down a hill at race pace.