In truth, Malc, there never (ever) has been any loyalty, and insurance companies simply sell a product. If the customer likes/needs that product, at the price quoted, then it's a sale.
Basically, it's back to supply and demand, of course.
Now, there are loads of variables (risk factors), which include driver gender, age, location, accident record, driving record, police record, occupation, required mileage, and a few I won't know about. But there's one that's rarely talked about - and that's the insurer's own 'spread of policies' budgets. Most insurers will have a portfolio of 'types of risk' - and may well aim for a balance of age/gender/location (etc) policies. Once they've filled their chosen number of a given type, they'll often load an higher premium ... (Just like a builder that quotes for a job, but doesn't really want it - he'll quote a higher price - (and be happy to do it with extra profit).
And, of course, since the introduction of online policies, including a fair old number of cowboy players, it's muddied the water even more.