Sure, but physical attacks with the aim of stealing bitcoin aren't happening by approaching random people on the street in the spur of the moment. The attack is targeted and planned, and the attacker usually knows the victim is holding a significant amount of bitcoin. Often they are home invasions, or fake meetups under the pretense of trading.
Unless you are involved in these types of attacks, you do not have any way of knowing this. These types of attacks are not well publicized.
You don't need to be involved in bitcoin attacks to realize that approaching random members of the public and threatening them to "hand over their bitcoin" isn't exactly going to net you high returns. Bitcoin attacks are planned in advance. I would also direct you to this page:
https://github.com/jlopp/physical-bitcoin-attacks. Sure, many are not publicized, but of the ones which are, the majority take place within a building (usually a home or a predetermined meeting point), or sometimes within a vehicle. More rarely the victim is abducted.
These attacks are not akin to a mugger approaching a random person on the street, and running if they don't have anything of value on their immediate person.