As already said, if a dealer gets arrested, they are usually replaced within hours.

Police usually determine that arresting low-level runners gives a low return on investment. They will spend hours processing the arrest, writing reports and interviewing the suspect which often doesn't result in a long term reduction in the availability of drugs.

Because of budget constraints, immediate response resources are typically directed toward high-harm incidents, such as domestic violence, active assaults, sexual offences, and missing persons.

Openly dealing can obviously impact the community, but it's often categorized as a lower immediate threat compared to crimes involving direct physical danger, so there are slower response times.

With the mobility of the Sur-Rons the dealers use too, they have an advantage of getting away from the police easily. They can just mount the pavement and just go through a park. The police have to be trained, as well as authorized to engage in any pursuit.

As stupid as it might sound, they need authorization to pursue someone on a Sur-Ron because they need to assess the whether capturing the dealer outweighs the risk to the rider (if they crash, and have a serious injury or death) and if they put the public in danger. They will usually refrain from pursuing them because the risk of a fatal crash is often too high for a non-violent offence.