I suppose I should say, why aren’t people more polite, because there are more polite people in the world than not, right? I hope so.
Politeness is an art. It is a skill. It is a learned behavior. Ahh, that’s the root, isn’t it? Politeness is learned, and like anything, you must choose to learn it. And practice it until it becomes second nature. Ever try to learn something that doesn’t interest you?
Think back to your school days, or if you are still in them—listen up. Didn’t like math? You probably got a B or less. Think that Language Arts is boring? Well, you won’t be writing any novels, will you? Dreaded Phys. Ed? Squeaked by, didn’t you? But if you try to do better in something, you will improve.
All behavior serves a purpose. If you can get what you want without being polite, then why be polite? If it makes you feel good to open a door for someone or say “Excuse me” if you bump into someone, then you are going to do it. If you can make someone’s day by being polite, isn’t that worth it?
You are not going to injure yourself or feel bad by being polite. Will it inconvenience you? Probably not, but it might in rare cases. Is doing the right thing worth it? I think so, but if not, it’s still the right thing to do.