If you meet someone in your daily life, at least you know whether there is physical attraction. This is fundamental in dating.
But for online dating, you have to go out and meet the person. People are usually different from their pictures. You will find decent people, but when you meet them, you realize there is sth about their looks, or charisma, or qi zhi or fen du that does not appeal to you. So you may have to try many people to find someone who is decent and whom you are physically attracted to. Can be very time-consuming.
