Because we do things in our homes and not do them in public. One of these things is fapping. If you have nothing to hide at your home, you'll feel confident in public.
Well i felt like that when i was 16-17, i just played games at my home, fapped, was on phone all day and didn't go out. And whenever my friends or my brother called me to get out i did and i was looking at them and saw how they all chilling and i was like in tense all the time. And when i have a opportunity so say something it always went bad and i felt worse and worse. Then a miracle happend, i joined the gym, made some habits like everyday before bed i do abs, reading on internet about medicine (you can choose what you like), played less games on computer. And it went good but not too god. After that i did cold showers, throw away sugar and drinks (drinked only teas and water), started gaining good muscle, started mewing (getting jawline, better stronger face). Then i was very comfortable with myself and talked easier to other people, started approaching girls when i was going out. Still there was something left to do and then i did Nofap with about 19 years old. My muscles are going crazy, i look good and strong, started reading books before bed and man i can tell you if you follow these steps when you go out in public you will be confident AF. Try it, it takes time but its the right way. Dont have fear about girls they want you badly when u fix some issues on you. Hope it helps !
Proper tongue posture, it helps you to lose chubby face, getting u that strong jawline and also cheekbones. Search it up its very strong, im doing it for about 4 months everyday 5-6 hours while im doing something and got some results!