>>ROI on some training and awareness would be far higher.

Motorcycle people generally spend money to placard their cars up with "Watch out for motorcyclists!" stickers so unless you're insinuating the government should use public funds to educate drivers on checking their mirrors and not getting into accidents with motorcyclists I'm not sure what you're actually saying.

Training quantifiably lowers risk - I'm talking about training for motorcyclists. We all have to do some training pretty much everywhere in the world before we become licensed drivers and riders.

In both the UK and US, advanced training courses are available and are recognized my insurance companies who offer discounts.

Anecdotally, the people that I've picked up off the highway have all been on a cruiser-style bike, been wearing improper clothing (usually shorts and T-Shirts) and not been wearing a helmet. Now that's legal here in CO and fine for an individual to make their own decisions. With further training however, you can make better decisions particularly around risk assessment and handling characteristics.

[edit - typo]

OK but individual motorcycle riders are not in a position to train and raise awareness in a way that makes them safe. So from the rider’s perspective, there is no good alternative.

While that may be true there are plenty free or close to free resources on the internet on in libraries and plenty of local friendly groups that often have a focus on advanced riding.

For the folks who are riding around on $20-40k worth of bike with illegal and noisy aftermarket pipes - that they paid for - it's not really an excuse.

It’s not either-or. There are situations where advanced riding will not protect you, but being more noisy will. Plenty of disciplined, advanced riders also choose to be noisier with aftermarket addons, especially on smaller bikes. It’s a trade off that riders make between increasing their safety and being less obnoxious. It’s reasonable as a pedestrian to be annoyed at those that choose the former, but you can’t just dismiss their decision on the grounds that it’s useless- that’s objectively false.

When I used to ride all my problems with other motorists came from people approaching me from behind or to the side, not from me coming up behind people (perhaps because I was not in the habit of lane splitting at every opportunity). I suggest a horn serves the same function without annoying everyone nearby and eventually deafening the rider.

Being heard can help with cars approaching from the side, for example a car moving into your lane while failing to see you.

It’s not a silver bullet but it’s one more layer of safety and I don’t understand why that statement is so controversial? I’m not even advocating for these after-market mods (I don’t use one) just pointing out that there is in fact a tradeoff.

Now, some riders just like being loud for the sake of it, and that is a whole different story.