Wearing diapers as a teen, child or even an adult is perfectly okay even if you do not really need them for protection.
Some people wear diapers when on a road trip so they do not have to hold in their pee when a restroom is not nearby and many people even wear diapers when at events such as the New Years event in New York City.
Diapers can be very convenient and we all wore diapers as babies and toddlers and if you need too or want to wear diapers as a teen or adult you certainly can and there's nothing wrong with that.
So if you like to wear diapers or just want to wear diapers for a just in case there's nothing wrong with doing so.