That would have to be negotiated in the Police Union contracts. Same reason they can’t fire pedo teachers immediately, they are contractually obligated to keep paying them until they are investigated or found guilty.
Most of these cops “retire” to end the internal investigation and keep their benefits, then decide to “unretire”, and get hired in the next town with a clean record.
The police have one of the strongest unions in America, and almost no one bats an eye. But let Starbucks employees try to unionize and you’ll hear how greedy and corrupt unions are.