They don't have to, at least not for many viewers like Firestorm, who include this option to avoid loading textures with an amount of pixels beyond 512 px :
... and they will not do such as you suggest, because ... money ? ...
Well, Wilhiam apparantly became the OP of this thread, whilst I'm certain it was not started by him ( it was Storm Clarence, I think ), because ... he is me.
If you didn' t know.... now you know ..