There’s two distinct scenarios where bad driving is involved.
The first is where sustained and deliberate furious driving takes place, often accompanied by a pursuing police car and/or helicopter. The vehicle may be stolen and/or other serious offences may be involved such as insurance deficiencies or disqualified driving. In these circumstances, the threat of a fine (which, if it is paid at all, would be at a fiver a week) when the other offences attract custody, or the prospect of six points when the other offences attract lengthy disqualifications are hardly likely to attract much response following a request for driver’s details.
The second is more what I had in mind when I looked at this question. This is where careless or inconsiderate driving is undertaken when other aspects (insurance, licence, etc.) are in order. Imagine this: I get a dashcam image of some bad driving. Apart from capturing the vehicle Reg No. it (unsually) also happens to capture a decent image of the driver’s face. I report this to the police. They (even more unusually) decide to follow it up. I don’t know the driver’s identity and neither do they. What do they do? Prepare an article for “Crimewatch”? Put out an “all ports warning” with photos of the miscreant? No. They send a S172 notice to the Registered Keeper requesting driver’s details at the time of the incident. This time the threat of a hefty fine and points often concentrates their mind (especially if they were not driving themselves).