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

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?

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

New satellite constellation will scan the entire Earth every 20 minutes to find wildfires - Space

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

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

THE BIBLE IS THE PROBLEM!

Have you ever had sex with your female cousin? How did it start?

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?

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

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

Can the United States threaten the UK with destroying its economy to force it into anything, just like what happened in the Suez Crisis?

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.

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

A belief in a god is not the problem.

Are there any good YA romantasy/regular romance books for Christians? (preferably romantasy if possible)

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