Just because caravanners are only occasional drivers with trailers doesn't mean they shouldn't be tested on them - quite the reverse. there are different speed limits, reversing techniques etc. The number of car drivers that I've seen who don't realise that they've lost control of their trailer, or are hoping that the trailer is intelligent enough to bring itself under control is nobody's business. That is why you now need an additional test to pull atrailer of any size.