Granted - A LEO can always sit tight until backup arrives, but, a lot can go down in that time.
A partner and/or backup brought more "firepower".
Still ---I recall a story I read back in the late 1970's in one of the gun rags about a cop in Florida that happened on a group of drug dealers armed with MAC -10's. He escaped, but, it was touch and go.
His letter to the editors was more of a plea to get rid of the revolvers and at the very least, give them some kind of chance of meeting "fire with fire".
Not too many years after that, the Cleveland Police Department pleaded with the public to write letters to the Cleveland City Council to get rid of their revolvers and go with a 9mm.
I was more than happy to pitch in on that.
You cannot always sit tight and wait. If people are being hurt you cannot wait. What people fail to comprehend is that every bullet has a price tag and a lawyer attached. We are responsible for every bullet that we send out. Many people here seem to think that with a hi cap pistol it enable them to send out a stream of bullets. That is great, except those sprayed bullets rarely hit the intended target, and when they do they generally fail to stop the target. I was a cop in revolver days, one of the cops I worked with in 1982 carried LSWC's in his 357.
Police do not need hi cap pistols, they need better training. That being said the 357 magnum is the upper limit for most people to be able to handle. I worked with one cop who could drill out a hole with 38's, but as soon as he started using magnums he could not hit the target. He had to carry 38's.
A double action revolver is difficult to master, but once you do you can shoot anything.
The other benefit is that these days there seems to be a rush to judgement with officers who put multiple 9mm HP's in BG's. To be honest I don't think today's wiz bang bullets are that much better than they were 30 years ago, not if you judge how many it takes to bring down the average thug.
I am happy with my old school cup and core 180's @ 1450-1500 fps from my Smith model 69 in my semi retired lifestyle. Of course I do have an electronic rack with an AR Pistol in the trunk.