Age or inexperience?
New driver insurance tends to be rather pricey because most people getting behind the wheel for the first time are aged between 17 and 24. This is the age group most likely to be involved in a claim, so while you might be an excellent driver yourself, you are unfortunately let down by the statistics showing that many similarly aged motorists are sometimes less than careful.
In particular, young males have historically had a hard time getting insurance quotes that are affordable to them as statistics suggest their females are safer drivers. As of 2012 though, insurers throughout the EU have been banned from factoring gender into their pricing. Even people throwing away their L-plates later in life sometimes get a raw deal though. They might not be eligible for a no claim bonus, so they will often be viewed as an unknown risk by insurers.