Assuming cops actually present the evidence they have and don't hide it from the defense. The police and DA don't care if they put a guilty or not guilty person in jail, the 'tough on crime' faction that tends to get people elected cares about the number of people thrown in jail. The more the better. Throw 10,000 people in jail, you must be a damned good elected official and you get re-elected.

>you can't have more arrests without the means to do so.

Not exactly sure what you're trying to say... you can always have more arrests. Make more things crime. Pre-crime, thought crime, speech crime. When you run out of physical space you start stacking the prisoners 10 deep. When that runs out of space you start executing them and putting them in ovens.

What I was trying to say is that if no one is available to make an arrest, you can't make an arrest.

Why do you think people get away with minor traffic offenses all the time, something right in front of an officer? There simply isn't enough means to deal with these, so they just ignore most of them.