Hello Mel,
That's an clever question! which camp do you belong to?
Too much choice or not enough?
If there such as thing as a perfect design, everyone would be using it, there would be no need for choice, but it is easy to see that a one design only scenario could not work, simply because caravanners families are not all the same size. I know that's a gross over simplification, but it illustrates the point there needs to be choice.
As with almost everything we do, we like to be a little different, so again choice is important, and it can be just little things (not just children and rats)that upset some people more than others so a sense of being able control or change your environment by making choices and personalising it is seen as important.
In theory each caravan manufacture would like to think they can offer enough variations and options to cover the wildest dreams of Mrs & Mrs All Public, but that is of course is impossible, but add in the variety of options that each new manufacture brings and that impossibility factor reduces.
However there are only a limited number of possible basic internal layouts largely dictated by the size of beds we need, and the maximum dimensions a caravan can be, and the limiting factor of the towing capability of vehicles. So across different manufacturers you will find many of the same themes appearing.
Where designers in the UK have tried to step outside the bounds of convention, the designs, I suppose by their nature, have tended to be esoteric, and it does take quite a lot of bravado to convince a very conservative public to buy avant-garde products.
It doesn't help that such offerings especially from new manufactures tend to be rather expensive which puts an inevitable brake on sales.
But that cant be the whole reason:- I recall many years ago one of the mainstream caravan manufacturers did invest in a very leading edge caravan design (I think it was Avondale). Despite its selling price being held low to attract customers, I believe they took no orders, and only sold the two exhibition models.
I do find it annoying when exactly the same product in every detail is offered under two brand names by the same manufacture. for example do you remember the BMC Austin and Morris mini/1100/1300 ranges? and in more recent times even different manufactures have shared identical products such as Renault and Vauxhall commercial vans. Others have used the same basic shell and customised them such as the Mk1 Ford Galaxy, VW Sharan and Seat Alhambra etc
One can feel 'cheated' in some ways, but by sharing development costs and common components helps to keep costs down, and the same would apply to caravans. So expect to find caravans with shared designs and features across different ranges.