system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why your lips get chapped. I’ve always thought it was from your lips being dry and also has something to do with cold air. If they get chapped from being dry, why wouldn’t adding water to keep your lips moist solve the problem?
gpt
Just adding moisture to your lips doesn't last. Our skin has oils in it to prevent evaporation and water loss (and help resist obsorbing too much water) and dry lips also lose these skin oils. 

An oily or waxy substance will help lips retain moisture as opposed to a watery substance which will make them wet briefly. And of course lip balms are waxy substances for this purpose.