Simple answer is cost and the ability to get the public to part with their cash. However, Tamiya may be bucking the trend as their 1:32 Spitfire has been so well received in the modelling community. It initially came in for some flak as it costs around £89 which initially sounds a lot. However, to get the same level of detail on any other kit, a huge investment in photo etch and resin would possibly make any other build around the same price. The real benefit of the Tamiya kit though is the sheer quality. and innovation. The magnets that build into the kit to enable the engine covers to be fitted without glue so that the super detail Merlin can be shown off is very nice as they are invisible to normal viewing.
The scope for third party super detailing for this kit could take it to another level if anyone wants to but I doubt it needs it. From what I have read on the kit, there are unused parts which hint that another Mk will be released at some point sharing the basic sprues. No one knows if Tamiya can corner a market with other releases in the same scale and quality but if they can make them so good with such high detail and lack of need for third party add ons, they will be onto a winner. The obvious kits to follow up would be a P51 and an ME109. After that, the Pacific aircraft would be welcomed, especially if they release new paints to go with them as they did with the Spitfire. Producing three new colours for the two greys and the green show a real commitment to me.
Not sure if any other manufacturers have the nerve to try something similar as they would have to be just as good. Don't forget the Airfix new Mosquito which retails in a lot of places at £132, making the Tamiya Spitfire quite cheep. For me, the big issue is not so much the cost, not because I can afford them easily because I cannot but the Tamiya Spitfire realistically is only the price of a couple of the newer Tamiya Armour kits. The real problems for me is storage, If I built them, I would have no where to display them.
Not sure