It is of course a matter of personal choice what vehicle a person wishes to own, however these days with diminishing personal disposable income, and so much uncertainty about jobs etc, increasingly many people actually look more carefully at the balance between wants and needs and what finances will allow.
The vast majority of the time caravanners do not need the capabilities, the complexity and expense of a 4x4. There are far more solo road miles than towing miles, so most could caravan perfectly satisfactorily with a larger saloon or an MPV.
The argument that we need a 4x4 for when we need to get on or off a site is often over stated and the majority of caravanners never use sites where there is any problem of access. There are some who do choose more awkward sites, but most never do.
The cost of ownership needs to be considered, and generally the bigger vehicle the more it does cost, on fuel, servicing and insurance, and depreciation.
A factor that is becoming more prevalent is the effect of the licence category changes that were introduced in 1997, We now have drivers in their thirties who may be considering moving up to a larger vehicle, and yet may not be aware of the 3500Kg outfit limit their licence places on them. A 4x4 may be desirable but impossible because of the combined MAM of outfits exceeds their limit. So the "e" extension test is another cost to consider.