Birmingham Anglers Association

It would seem that, and on the face of it, the close season, in main, is to protect spawning.
This then begs the question; why is it that the majority of canals and stillwaters are open to fishing? Are all the fish eunuchs (lol) ?
Leading on from this, I would ask why Scotland and Ireland do not have a close season?

Maybe somebody with a better understanding could enlighten me, as I am completely at a loss as to understand the why and wherefore of it all.