What incentive does any big manufacturer have to make new racing bodies?
There's plenty of choice for bashing and drifting because the body aerodynamics aren't important, and people want a wide range of bodyshells, so you have ABC Hobby, Chevron, Deltaplastik, Speedway Pal, Spice, Yokomo, etc as well as Tamiya and HPI who all make a wide range of different shells for the bigger non racing market but none really suitable for high level competition.
If you want some choice of racing touring shells then the small scale racing companies like McAllister and East Coast are going to be the ones to do it, but their market is entirely people who deliberately want to be different to everyone running Protoforms.
For racing the Global Body Spec means there's no incentive to develop different bodies any more. 10-15 years ago they were experimenting with different shells to see what worked and what didn't, bringing out different designs roughly based on real cars and finding out through sales as to what shapes worked best.
Now we have the GBS and ridiculous licensing fees so we have standardised to no name shells that are all roughly the same shape. Protoform dominates the racing class with a selection of bodies that cover just about any track so they have no incentive to make anything else, why pay out to develop a new body when the sales of the new shell will just mean sales being taken from other bodies in their range. The GBS means a small body company can't come in with a new body design that beats anything by Protoform on the track unless they are really lucky, if someone did make a better body and Protoform started losing sales then they would quickly get a new one out.
It's like in 1/10th off road, where everyone is asking why Associated doesn't bring out a new 2wd buggy because everyone else is. The answer is why spend a fortune to replace something that is already dominating the class.
As for HPI, what interest do they have in producing 190mm bodies? The only 190mm car they make is the TCX. The Nitro RS4 and electric Sprint2 are both 200mm wide as standard. HPI still make a good selection of 190mm race spec bodies under the Moore-Speed brand (
see here and scroll down) but I presume being developed and made by HPI Europe is why they aren't sold in the US.
Manufacturers constantly bring out new high end chassis because that's how they make the most money, cars aren't consumable and regularly replaced like bodies are so to keep selling cars you have to keep on bringing out new ones. Look closely at them though, for example Tamiya regularly update their TRF cars but almost everything that changes are machined parts, a few tweaks in CAD and the next lot of parts machined out mean a narrower chassis, lower/higher top deck, etc. all parts that have no tooling costs. Yet they are still using plastic moulded suspension parts that go back to the TA04 which have high costs for making a new mould.
With bodies the main cost is in developing and producing the pattern the bodies are taken from, the production costs are relatively small so the more bodies pulled from each pattern the cheaper the bodies are to produce. Unless a manufacturer sees a need for a new body and they expect to sell enough extra shells to cover the development cost, they won't make them.