If we arm everyone, then everyone is part of the militia and we no longer need a standing military. Effectively, everyone will be required to purchase their weapons and be drafted to serve. Imagine all the money that can be saved by recalling all troops (restoring to them to militia status) and closing all bases, foreign and domestic. We will store all arms in armories across the country. After all, the founding fathers did not trust standing armies and preferred militias. 

And while we are at it, why do we need police? FBI? CIA? SEC? FDA? EAA? NHTSA? 

We all will be richer by not having to pay taxes and in full control of our own safety!