The VIRM double deckers in the Netherlands used to have those food cart elevators. Interesting to hear those are still in use in some parts of the world. The food cart service on our intercity expresses was removed, so in the course of the years those mini-elevators were taken out as well during scheduled revisions of those EMU's.

Now some third party is allowed to provide a mediocre rail catering service, which amounts to students doing a side-job wearing backpacks with hot water and cups and a tray filled with instant coffee and tea and a few cans and packets of crisps and cookies strapped to their bodies making the rounds at seemingly random times and places on the journey. Not quite the same…

Add to that the lack of the frankly brilliant concept of can-coffee (缶コーヒー) from vending machines on the platforms and eki-ben (駅弁) and I suddenly really miss the Japanese train experience.

No problem except it was built without elevators...

That's easy to do for a new line but pretty much impossible for existing lines, because the clearances are not tall enough to fit a normal double decker train where the first level is at existing platform height. (In the current ones, you step down to the first level.) It would be hard to retrofit tunnel heights and bridges after the fact. You also run into the problem where these special trains are only permitted on parts of the network and stations that can handle them, which severely limits their utilization.

It's why even basic iterations of technologies requiring modification are often market failures, like the A380 requiring special gates to handle it. Boutique technologies like monorail or maglev fail even harder. For most cases it is profitable to use the less optimal but more flexible solution.