Arrest Warrants: Why Would the Police Choose Not to Arrest Somebody With a Warrant

My question is about Missouri misdemeanor warrant it is a few years old completely forgot about the fine. I was pulled over and the officer ran my name and told me about the warrant but never arrested me for it weird I thought the warrant is from a town 3 and a half hours away from where I live is that why they never arrested me for the warrant? I plan on paying that fine I forgot about next Wednesday when I get paid but I was curious as to why they didnt arrest me that evening on the warrant

Arrest Warrants: Why Would the Police Choose Not to Arrest Somebody With a Warrant