Why does he like PDA?

My boyfriend doesn't see a problem with kissing me in public and can't figure out why I don't like it. Sometimes i have walked away from him when we say goodnight because I hate PDA. Most guys hate it more than girls I thought. Why does he not mind it? It's weird to think that I'm the one who doesn't like it. Most girls would find it cute or whatever. However, I do not. I find it embarring.