Mains Water Closet direct Flush valves still a rarity in UK?

[whitegold]

Just was at a caravan site in Lake District recently, which had some very interesting Delabie electronic tap and shower fittings, also direct WC flush valves which worked extremely well.
Always wondered why these valves didn’t seem to catch on in UK when very many other countries never use cisterns.
A quick look in the Delabie specs sheet reveals their valves require a 20mm bore feed capable of around a litre per second.
Any gems of wisdom out there? I have put on a hard hat in anticipation of the expected responses

 

[ShaunCorbs]

Basically most of our toilets were tank fed which was suitable also it’s fun as they need to be fed from a break tank and pump due to the backflow issue

 

[snowhead]

The Caravan site may well have had direct flush valves, but if you traced the source for that water you'd find a storage tank and pump.
Many countries have water that is undrinkable from the mains and many countries have water supplies from local boreholes / wells / springs.