why do most airlines configure 777s in 3-3-3/2-5-2 and not 3-4-3?
there are some airline that ordered 777s in 3-4-3, or converted to
3-4-3 recently....

3-4-3 on a 777 usually have identical pitch/width as 3-4-3 on 747s....
(which means they are equally uncomfortable on long flights)