Confidence comes from experience, practice and a friendly environment with others to help build yourself up. You can't just summon confidence out of the blue especially for people who never was able to form confidence in oneself. It takes time, effort, energy, courage etc. just to build enough confidence to asking some random guy or girl out you hardly know which is a battle in itself. It puts a lot of pressure on your vulnerabilities trying to put a mask on and essentially not being able to be ourselves. Plus not everybody has a very exciting and social life, have any hobbies let alone enjoying anything in life period and because of this the potential relationship that may follow will be made up of lies just so you don't present yourself as an boring outcast. Talking to girls? Talking itself? That's laughable especially for people who can't keep a conversation going past the initial encounter. You have to talk about specific things (no depressing/morbid topics) and of those things you talk about you have to have an interest in it just to keep the conversation going. It's a ripple effect, a never ending battle until you run out of things to say. And that's the tip of the iceberg here. The anxiety, the self hatred, the inability to effectively communicate with other humans, financial stability, background, job security, future goals, humor, looks (yes looks are a major factor), etc. so many things add up that determines your success.