I can imagine they're personally motivated to try and resolve things without resorting to arresting someone as that would result in paperwork/processing/etc back in the office.
It's not too uncommon to see police get involved in negotiating disputes where there's no specific powers they can exercise (other than removing/arresting the person for trespassing/breaching the peace/failure to obey a 'move on' order).
Have the cops turn up makes both sides treat things a bit more seriously - the store manager wants them gone ASAP to stop making a scene, and will be more likely to do whatever it takes to escalate the issue to someone more senior if the police ask.
Remember: If it's in the news it's rare. This means that Police violence in America is rare, and Police negotiating with an ISP is rare.
https://en.wikipedia.org/wiki/Police_firearm_use_by_country#...
Per capita, at least 5 times more people die in the US from police firearms compared to similar countries. Compared to Australia, its about 80x (per capita).
The issue with police shooting deaths is not that there is a high likelihood of an individual dieing tomorrow (for reference, drunk driving deaths are 10x police shooting deaths [1]), but the injustice of innocent people being killed.
Accurately representing the problem, and avoiding the "all police are terrible" comments is vital to actually trying to fix this, as a solution necessitates actively working with police, the vast majority of which have not, and will never, shoot anyone.
[0]: https://www.bjs.gov/content/pub/pdf/nsleed.pdf
[1]: https://www.cdc.gov/motorvehiclesafety/impaired_driving/impa...