Thank you for pointing this out. Head phones are a huge problem with this, as well. I have seen a stupid number of stupid pedestrians walking or running with earbuds in, or hunched over on phones, or some such.
Do you also contend that people with hearing impairment should not be walking?
To analogize, I believe you ought to avoid unnecessary medical treatments, because each presents some kind of risk. If, however, you need treatment, I suggest you receive it (though it will carry a risk). By the same token, if you can walk carefully and observe the world around you, you ought to. If you need to walk and cannot see, it's fine to just accept that certain things carry risk.
Hearing is arguably more useful in many situations, as it is omnidirectional. I can hear a car coming from behind me; I likely cannot see it.