In my experience, night trains with private cabins are fan service for rail fans, environmentalists and/or masochists, not real transport options.

One of the famous sleeper trains in Europe (Nightjet Vienna-Amsterdam) is often booked out weeks (sometimes months) in advance, costs as much as a plane ticket + hotel room or more, and you have a decent chance of being told (as you show up in the evening) that unfortunately one car is missing tonight and you have the option of a full refund (screwing up your entire trip and having to book a last minute plane ticket), or you can take a 50% refund on your 255 EUR sleeping ticket and spend the night sitting in the shared seating part on a seat that would have regularly cost 35 EUR. This was something that on some routes was happening routinely for over a year [1].

The night train from Switzerland to Malmö was cancelled (after tickets had already been sold) because the Swiss government decided to not subsidize it.

Trains like this offer zero flexibility (you have to book a specific train weeks in advance), go where they go which is a very limited route network, and even in Europe with all the environmentalists, rail networks, shorter distances, and massive government subsidies, they don't seem to be able to run them very frequently or on many routes.

Calling them equivalent or a replacement for self-driving cars (which would take the passenger where they want, when they want) is disingenuous and isn't going to magically convince people.

[1] https://www.srf.ch/sendungen/kassensturz-espresso/espresso/f...