Or punch people in the back of the head while they are lip-locked. let's see how they will like that.
see what happens if you park your car in the middle of the freeway. you will be smashed into by sixteen different drivers, your car will be totaled, and then the police will come and tow it away and then give you a bill for the service as well as press charges against you citing you solely responsible for all 16 other drivers, and your insurance company will raise your rates so high that you won't be able to afford to drive anymore.
Why should it be any different in circumstances of foot traffic?
I'm not against kissing or other affectionate gestures; if you want to get a hand job at the train station or the super market I'm all for it, provided that you can walk and get jerked off at the same time.