In Texas if a Non Prosecution Affadavit was signed and the victim does not want to pursue why wont the DA drop the case?

Because in the State of Texas the halls of justice are painted green. I have just been through the same thing. I was horsing around and playing a joke on a mutual friend of mine and my wife's and the Pflugerville (Travis County) police pulled up and accused me of destruction of public property. I was ultimately charged with a class B misdemeanor (considered a crime of moral turpitude which does NOT look good) and taken to jail. Even though I had a signed affidavit and our friend refused to testify the prosecution absolutely refused to drop the case because it was the county that filed the charges and they did not need her testimony to pursue further action. All it boils down to is money in Texas. They want your money and they don't care how they get it. Even if it means doing the wrong thing and hurting someone. Your best bet is to have your attorney speak with the prosecution (DA) and plea down to a class C misdemeanor depending on your alleged offense. Then, you will be able to have the arrest and the charge expunged at a later date. I believe it is now two years before you are eligible for expunction. Best of luck and get ready to bend over for Texas. I know I had to. And they DON'T use any lube when they bend you over. :(