I'm not quite sure of your ...

I'm not quite sure of your point here. The choice of a meter for any application is always a compromise between many different factors - including performance, cost, reliability, expected service life etc etc. The rotary piston meter we tend to use in the UK has evolved as the (current) meter of choice because it does a pretty good job of balancing these compromises. It is relatively cheap, will last typically 15 years (admittedly with some degradation of performance but that happens with any mechanical meter), is reasonably robust, it has good low flow sensitivity (which is important where much water supplied is stored in tanks with ballcocks to control inflows) but also has a wide measurement range  - wider than most other meter types. This minimises the number of different sized meters required to cover properties with different consumptions, making installation simple. Importantly the impact of mechanical wear tends to be in the customers' favour, i.e. the meters tend to under-record over time. This means that there is no need for regulation around replacement tor expensive testing programmes driven by consumer protection that there is in countries that use technologies that are likely to over-record. We also like putting meters in boundary boxes underground and outside - few other meter types have been developed as manifold fitting.

Whether these considerations hold up as solid state meter types begin to penetrate the market remains to be seen...