Mindfulness is a therapeutic technique used in contrast to the state of semi-consciousness many people get buried in as adults. It is not something that anyone I know of “advocates” as if it were something to do all the time and never be any other way.
“a mental state achieved by focusing one’s awareness on the present moment, while calmly acknowledging and accepting one’s feelings, thoughts, and bodily sensations, used as a therapeutic technique.”
I don’t know what sources you are looking at, nor what you mean about texting/talking while crossing/driving. Those might be examples of having your attention on something other than what’s going on around you in a practical situation – an example of non-mindfulness being dangerous. I suppose it is true that people who don’t practice mindfulness or meditation may be more prone to being lost in thought or mobile phone activities without noticing they’re in danger, but that seems like a distracting example.
I think you’re confusing instructions for how to practice mindfulness exercises when doing nothing else, as if it were telling you to do that all the time and never think in other ways. No one advocates that, except during an exercise. Someone might try it for extend periods if they were going to go on a meditation retreat, but it’s not a suggestion for what to do to an extreme degree in modern life all the time.