its not reasonable because the only way kids or anyone learns these things is by experiencing them. and the earlier you expose them to these situations the better they cope and eventually understand.

its not like magically one day they are old enough to just "get it" by being explained. when was the last time you really understood something only conceptually without any kind of experience with it. its the jobs of parents and society* to safely expose our kids to the situations that they need to experience to learn how to function on their own.

Like to use the airplane example its not like parents just do it for fun and also every parent does stuff to try and give their kid the best ability to cope with the pressure change. snacks, pacifiers, timing flights around naps. its not like they are just like "eh, suck it up kiddo".

*there is a much longer diatribe about how even if you don't have kids or hate kids or never want to be in 100 ft of a kid its still your responsibility to society/biology to help make sure the next generation is raised. And maybe you could fulfill that responsibility at the literal bare minimum by managing to have a little compassion and understanding and not rag on parents who are (even by choice) doing something really hard with their kids. (flying)