[Planktonne]

Making sure you are fully aware of your surroundings is prudent, in case someone is acting recklessly or maliciously, but it shouldn't be a requirement.

You're not to blame at all when a cyclist runs you down on the pavement (that they shouldn't be on). Yes, you might have heard the bell without the headphones, but they're the one acting recklessly, and they're the one responsible for ensuring that they don't harm people acting normally.

There are all sorts of situations that it's possible to anticipate, but there's no moral fault ascribed for not acting defensively against every possible form of attack.