Why does it matter so much to atheists that God doesn't exist?

Because these are not any gods rules we are talking about.

IT does not matter, mainly because it does not exist.

And then use and ENJOY these fantastic scientific advancements every single day of your life?

Is it possible for humans to determine their past life as an animal? Is there a scientific method to prove this?

And how do you deny hundreds of years of advancement in all fields of science?

A belief in a god is not the problem.

My problem is that people who try to shove their rules down everyone's throats - including by physical force - DO EXIST .

My wife admitted to cheating on me with a married man. Should I tell this man and his wife that I know?

Notice that I said their rules, not any gods rules.

The people of the modern world have evolved past all of that nonsense.

These are man made rules - made thousands of years ago for the use of the humans who lived thousands of years ago.

What is the recommended frequency for using a red light therapy device for skin?

Those rules that you are trying to reinstate are rules made by men who didn't know anything about the earth, nor anything about all of the other inhabitants of it. How can you not see that?

I do not personally care if you believe in a god or not.

I am speaking to the US Bible thumpers here, of course ~ many of whom are flat-earthers who deny evolution and see scientists as evil people who are constantly trying, and succeeding, in disproving their beliefs one by one.

Pokémon Cafes To Serve Incredible-Looking Plate Of Food That Can Mega Evolve Before Your Eyes - Kotaku

THE BIBLE IS THE PROBLEM!