You're serious? What you are describing is exactly what we pay our police forces, our national guard units and finally our military to do. But they operate under laws and regulations. We don't want to have to depend on some militia group that will eventually want to do a tad more than just protect our local law enforcement. They will want to create the law. It's human nature. Our Nation was created out of the power of the gun, but has sufficient checks and balances in it to give every citizen the right to change those laws he doesn't like, and make any changes to the Constitution and those in government without having to resort to life and death to do it. It's called a social order. The idea of law abiding citizens would soon die.
It's also how things used to work in many parts of this country. While there are some advantages to the more "modern" approach, there are some severe problems as well.
Among other things, there's not really such a thing as an "average crime day". On some days keeping the peace and catching crooks will require dozens of people. On other days, one or two. It is far more efficient to have ordinary people live ordinary lives on the days when a sheriff and a deputy or two can keep the peace, and have those people help the sheriff on those days when more people are required, than it would be to hire enough police officers to handle the bad days. The latter course of action will generally mean that even though there's not enough strength to handle the really bad days, it will be necessary to pay every day for police officers who most of the time have little to do.
You are correct that some time ago people got lazy and figured it would be easier to pay someone else for their protection than worry about it themselves. But that doesn't mean such action was wise.