Thin end of the wedge. Surprises me that people think that, if the majority of your drivers have these fitted, that the insurance will let them migrate to "traditional" policies.
I can hear the conversation now:
21y/o: I'd like a renewal quote please.
Broker: Certainly, ahh I see you've got a telematics box and a history of nice safe monitored driving, we'll only charge you a grand this year.
21y/o: How much if I don't want the box any more?
Broker: Why wouldn't you want the box? Are you planning on driving dangerously?
21y/o: No, of course not, I'd just like to know how much it would cost.
Broker: OK then, <tap tap tap> the equivalent dangerous driver policy will be three grand.
21y/o: Dangerous driver??? what the devil? I've shown you for the past four years that I'm a safe driver!
Broker: We know that. But you don't want a box anymore. We have to assume that you might want to drive (or end up driving) dangerously as a result.
21y/o: But I'm not going to!!!
Broker: In that case save yourself two grand and have the "safe driver" policy...
...and when we've all got them, say hello to road charging.
ETA: "what the devil"??? I didn't write that! I never knew the swear filter filtered mildly sweary acronyms!