As with many questions a theist may ask an atheist, the answer to this can be found by another religion asking it of you:

Why do you ignore Zeus? He's throwing lightning bolts all over the place and you're just ignoring him.

In the modern day, we understand that lightning is just the electrostatic breakdown of the air between the charged clouds and neutral ground.

It is not that you're ignoring Zeus. It is that you don't think there's an entity present to ignore. It is just a natural phenomenon.

When Christians, for example, cite something like Hurricane Katrina as a message from a god, atheists will similarly simply shrug their shoulders and say "What message? It is a natural phenomenon."

The message would be more convincing if it could be proven that it was actually from a god.