Atheists pay attention to religion because peoples beliefs and faiths inform their actions and other peoples actions affect us. For example if creationists are trying to get ID taught in schools then that's a big issue that affects all of us.
You're right in principle, if theists could keep their private beliefs to themselves then atheists would have nothing to discuss, but that's a fantasy that doesn't exist, there are all too many active theist groups who are trying to impose their beliefs on others and that cannot go ignored.
You're right in principle, if theists could keep their private beliefs to themselves then atheists would have nothing to discuss, but that's a fantasy that doesn't exist, there are all too many active theist groups who are trying to impose their beliefs on others and that cannot go ignored.