The being able to stop a serious criminal is just a bonus.
If someone is impaired enough to be driving dangerously, police will notice that and should pull them over. I'm talking about the minor infractions which (I presume) make up the majority of stops.
These practices also create a generally high level of fear and animosity toward police which isn't good for anyone.
"worth it" judgements shouldn't be made about what numbers justify other numbers if you aren't ready to have a priori numbers ready (as opposed to saying "this isn't justified because statistics" after the fact).
"worth it", "frequently", "risks"
These are all numerical arguments but you're claiming it isn't about numbers. Set a value for risk and reward and drive for that policy. Don't make vague arguments that lean on statistics when it feels useful but refuse to say when something is worth it.
What I see is kids getting shot in the street and my neighbors mugged and carjacked and police picking up guns in routine traffic stops. I don't think those are very "hypothetical".
It's like asking for "numbers" to justify not putting every 16-25 year old male in prison. It would drastically reduce the crime rate!
The numbers are: innocent people and police are dying needlessly, and any potential effect on the crime rate could also be achieved without those people dying through better policing strategies. It's pure waste.
People who commit crimes are probably more likely to get parking tickets too. Should police search the homes of everyone who gets a parking ticket since there's a slightly increased chance they'll find evidence of a crime by doing that?
Of course, they might catch a few mothers with prams on their way to said home, but that's a reasonable price to pay for not wasting so much time pulling people over!
Did anyone in the video get killed? Did anyone in the video go to jail? How many mother with prams do you think he would have killed?