I just thought it was logical that triggers would be appropriate for sprinting and player switching - It was the natural evolution of the staple of controls. Triggers for acceleration racers, shooting in FPS's and sprinting in footy.
EA was ahead of the curve on that trend. Conversely though, I always used the PES convention of

to shoot &

to cross on FIFA, even when they introduced the alternative controls on FIFA 06 on PS2, I was thankful.
Once FIFA indoctrinated everybody to have

for shooting on the last gen, I would always get treated like i wore underwear on my head when i had to swap my buttons around before a match with mates when they would just casually jump straight into it. I was Buzz Killington in the FIFA lounge.