Paid leave isn't meant to be a punishment. There is some expectation that police officers will inherently be involved in controversial activities that will require further investigation, some of which may legitimately reveal that the cop did nothing wrong. Paid leave is supposed to be a compromise to remove cops from active duty during the investigation (in case they are guilty, we don't want them still roaming the street potentially doing bad things) but also not be a punishment (in case they aren't guilty).
The problem is that said investigations always seem to drag their feet, never going further than the paid leave, and never seem to actually get to the things that are meant to be a punishment (firing, arrest, etc).