Comment by buran77

I still see ashtrays on older plans, trains, and boats. Sometimes older stuff is left there because it's not financially advantageous to replace it. You can use the recline button to your liking, but it can be inconsiderate to do it. Traveler discretion is advised.

A question you can always ask yourself is "should I do it just because I can do it?". It will stop you from being needlessly inconsiderate many times, and maybe even make you a better person.