It’s worth noting that most of these dining cars in speech are detachable, and as such the operator decides which train service it should be added to. For examp

It’s worth noting that most of these dining cars in speech are detachable, and as such the operator decides which train service it should be added to. For example in Poland, not all intercity services have dining cars. This allows to strategically increase the profitability of services where dining car is expected to be popular. I’d imagine that high-speed services operating the integral trainsets do not offer this flexibility, so they’d naturally opt for maxing-out seat capacity. Also worth noting that just recently the European Sleeper, a new contender on the EU rail map, introduced a dining car with an interesting fix-prix approach to menu. I suppose they estimated they could make it profitable, but notably, they too only offer it on some of the services only. The reviews on YouTube seem to praise the quality and overall experience. I personally think that night trains in particular will see the dining cars a necessity.