Fuel line and fittings

I'm a little confused here . I understand the 1/2" fuel line . I don't understand why the adapter to 1/4". If you wish to retain the factor tank outflow fitting right away you are restricting flow . NOw , if you are using a mechanical fuel pump with 1/4npt fittings , that is another restriction . You're not gaining anything . There isn't enough flow to feed the beast . 3/8" line all the way will do it .