Money. Space for a “gym” means space with no one it for take off and landing: so that’s an immediate drop in passengers. Similar issues for “bunks”. For it to work they would have to be bunks for the entire flight. That means you probably can’t use them for short haul flights (so your plane is less useful in general), you gain accessibility issues (people who can use seats may not be able to climb into upper level bunks. This is ignoring whether a bunk would be comfortable - you’re going to be constrained for movement (basically to retain passenger count there has to still be 1:1 bed->seat conversion, so beds would be as wide as a chair, and you’d need 3-4 levels of beds).
Then there’s safety - how quickly can you get out of your bed in an emergency is one thing, but how do you also ensure that no one stands on anyone while getting out, etc
Then there’s safety - how quickly can you get out of your bed in an emergency is one thing, but how do you also ensure that no one stands on anyone while getting out, etc