s.172 RTA (for endorsable offences) and s.112 RTRA (for non-endorsable offences) effectively require drivers to provide information to the police. If the police want to know who was living in the house you rented out, or where you transferred money to, or where the target of your mate's bombing campaign is, you can tell them willingly, or you can politely decline to offer anything, and the police have to get a court order.
A serious criminal accused of their serious crime can happily remain silent, forcing the authorities to do all the hard work. I'm sure many of you will have had the experience of reporting a theft to the police only to have them come back and say "Well, unless they come forward, there's little we can do." Yet if you own a car, you're expected to know where it is and who's driving it.
Why is this idea important?
A fraudster doesn't tell you how they embezzled the money – he goes free.
A murderer won't tell you where the body is – he goes free.
A terrorist won't tell you where the bomb factory is – he goes free.
A motorist won't tell you who parked his car overhanging a yellow line by a few inches – he is convicted of an offence under s.112 and faces a potential fine of up to £1000.
This situation is absurd, and clearly cannot be fair. It should not be an offence to be unable to help the police with their enquiries.