According to the FBI UCRs, around 10 percent of law enforcement officers who are feloniously killed on the job, are killed with their own weapons.
Not all people who open carry are law enforcement officers. But nearly all law enforcement officers open carry. And they
- use retention holsters, and
- have training in how to retain the gun.
Re the Serpa, why choose a stupidly bad design when there are so many other non-stupid ones out there? It's not like Serpa is the only possible retention design.