Loss of keys. If you expect the vehicle to be used by multiple different shifts then a lost key removes a vehicle from service unless you can reprogram it. Some cars let you program new fobs up to a limit then you need a dealership unlock to continue doing that.
Easier is just to key all the fleet vehicles with the same standard non chipped key. Then any key operates any vehicle which removes a ton of operational friction. When I drove cab we also just used fleet keys, but only because we bought old police interceptors, which also meant, our cab keys could open and drive police cars. Which is why police fleet cars sometimes have an extra interlock button or switch in them which disables the shifter so it can't be taken out of park. Similar to the switches in this post.
Vehicles assigned to a single officer may be different and will likely use the fob but the shift vehicles in a lot of jurisdictions just use fleet keys even today.
Easier is just to key all the fleet vehicles with the same standard non chipped key. Then any key operates any vehicle which removes a ton of operational friction. When I drove cab we also just used fleet keys, but only because we bought old police interceptors, which also meant, our cab keys could open and drive police cars. Which is why police fleet cars sometimes have an extra interlock button or switch in them which disables the shifter so it can't be taken out of park. Similar to the switches in this post.
Vehicles assigned to a single officer may be different and will likely use the fob but the shift vehicles in a lot of jurisdictions just use fleet keys even today.