Leaving aside the sudden outbreak of deja vu, and the sudden outbreak of deja vu, there are two reasons for reporting the incident:
1. Because you want the police to go and break the bastard's neck... or at least take some action to stop him doing it again. Probably you really want some revenge. Perhaps a slightly selfish motive.
2. Because you believe that, as Linford says, policing policy needs to be guided by reliable statistics. It's your public duty to report incidents like this. If you don't, you're in no position to complain when the police don't take any action.
I admit that I haven't tried to report this particular sort of of road incident. But I have reported various criminal damage to a building I'm a trustee of. When I became a trustee, I took a policy of reporting every time the building was vandalised, no matter how trivial the damage. Each time I was able to report it on the phone, I was given a crime number with no hassle, and I was usually telephoned back at a time to suit me for complete details to be taken.
OK, this took maybe half an hour each time.
But after reporting about a dozen incidents this way, the local beat officer took an interest, and phoned me up. We had several worthwhile meetings (usually in his van, slightly embarassingly...), and the upshot was that he caught the little scrote that was largely responsible. The scrote in question had to pay a fine, pay for some of the damage he'd caused, apologise to the trustees in person, do a spell of community service, and, had we wanted him to, we could have had him personally come and do some repairs.
He (and I'm talking about the beat officer now, not the scrote) said that he was amazed to find out the scale of the damage that had been occurring and how long it had been happening for - why hadn't we reported it before?
When I told him that the other trustees felt it would be a waste of time reporting it, he just shook his head in frustration.
Going off the point a bit, I know, but if no-one reports anything, the police cannot act. If they do, they at least have the choice, and can't defend their inaction by saying "well, no-one told us".
Finally, how are you going to feel if you don't report something like this, and find a week later that the same person has killed someone with his 4WD? Your action in bringing his behaviour to police attention might just have prevented that.