And insensitivity. That's why we put one person on guard so everyone else can go 'shields-down'. Dangerous situation requires an assigned responsible person whose job is to be heads-up for that time and empowered to raise alarms, order people back etc. I guess if this is some kind of "nature spectacle theme park" you need someone permanently around who is an expert on the situation and knows when to call it.

Not really. There are different levels of situational awareness. One doesn't have to be on high alert. Just being alert enough that you hear a pallet jack coming down the cross aisle is more alert than half the people seem to be.

As GP said, it’s hard to maintain that situational awareness on a constant basis.

However, it may be prudent to tune in when you are in a new environment or you hear a new sound in an environment you’re used to.

"or you hear a new sound"

What you've just described is situational awareness.

Maintaining condition yellow "relaxed awareness" should not be hard to do at all.

Maintaining any level of vigilance is still more exhausting than maintaining none at all, even if at some personal level you believe it shouldn't be hard to do.

Do you look before you cross the street? Do you turn to see what a beeping noise is that is approaching you in a store? Do these things exhaust you?

It's super easy to have basic awareness. Crossing the street is a great example because you need the awareness that you're near a street. Then the awareness to see if it has a crosswalk/light/etc. Then what the light status is (if applicable). Finally looking for cars.

People who lack any awareness at all are the ones you hear about falling in manholes because they were looking at their phones.