The only thing I can figure is that there is many more word walls than there is shouts, so it's possible to collect all the shouts without breaking the roleplay of your character completely in half. Any word on that from similarly minded players?
I really hope Bethesda isn't pushing us into making stupid munchikin characters that are good at everything. Fine if people wanna do that, but they shouldn't be encouraged into it, especially since Bethesda are going in the direction of specialized characters (resulting in the player making more than one) since they added perks to the series.