Politics. Money. Expediency. The cheaper and easier you make it to do something, the easier it is for you to get signoff to do it. Humans require oversight and

Politics. Money. Expediency. The cheaper and easier you make it to do something, the easier it is for you to get signoff to do it. Humans require oversight and care. A robot staking out an area? Not nearly as much, and folks don't get nearly as much backlash when a robot doesn't come back home.