Are there airlines that actually offer dine on demand in J? EK does offer it in F, as do most carriers serious about their F product. But then that is much easier when dealing with 5 people instead of 50!

It is also a question of keeping the cabin silent. On overnight flights, most of the J cabin would want to sleep, and one person eating would disturb everyone around them. So it's best to have everyone finish their meal and let them sleep.

In F it is different because with Suites there is little disruption to other pax.

I don't think it's just a question of whether it can be offered, but whether it should be, and the cost implications of doing so.