In fact, I would say in the police it's worse as they learn to dissasociate with people's problems since they see them every day.
Case in point: We were involved in a car crash. The guy crashed in to the side of us and span us 360 degrees. Immediately after the crash I checked on my wife and she said she was ok (I think she was in shock, though, later she had to be cut out of the car, needed oxygen, and was taken to hospital). I got out to see if the people in the other car were ok and saw them try and drive off, but their car was too damaged and they just drove into a few parked cars. I had a clear view of this. When the policeman arrived that night to take our statement it was clear he'd had a long day for whatever reason. I told him I saw the other car attempt to drive off.
"Are you sure, sir?"
"Yes. There were other people there, didn't they say the same thing?"
"No."
"There must have been damage to the other parked cars, though, what about that?"
"The only damage was your car and their car. Remember, you'd just been in a crash, perhaps you're misremembering?"
"But I could've sworn...."
"Are you sure you wish to pursue this? No one else reported this."
"Er, ok, er...."
It was only many months later, when we received the witness accounts from the insurance company, that we realised the witnesses said the same thing as me. Neither the insurance company not the police cared.
Maybe there's an extra form to fill in if someone tries to drive off.
Would people refusing to talk to the police actually make catching criminals harder? Perhaps. But that just means the legal system needs important simplifications. Also, the balance of power needs to shift in favor of the citizen.
So it seems like a good idea to play nice and make them be on your side.
I have forgotten the contents of the video in question, though, and I live in Europe. Might watch the video again.
In Europe maybe, but not in the US. You are not a cop so they will never be "on your side". They have cases they are pressured to close, so anyone coming in volunteering information is also showing that they know.
If you make a profile of a perpetrator of a given crime what traits will he have? First of all he/she will know all the details of what happened (since they did it). Someone who wasn't there and wasn't involved wont. So if you witness a crime and describe it to the police you've just proven that you fit that part of the profile. That would automatically make you the number one lead if they have nothing better.
And who knows? When I was a kid I did something I shouldn't have. When I saw a teacher was about to discover it I quickly "informed him" of what some bad child had done. I thought this would divert suspicion away from myself. That person going to the police and being "helpful" may actually be trying to divert attention from themselves, try to figure out how much the cops have figured out, etc. The cops can't know so the only logical thing to do is peruse the different leads according to which one is closest to the likely suspect.
And I'm not even describing the cops doing anything bad like framing people (which isn't unheard of).
That's like saying that a determined thief can always break in, so why bother locking your doors?
I can't explain it better than that. I might be wrong, too, when it comes to dealing with the police.