When the Constitution was written, gun ownership was not thought of as means of protection for a family. Gunpowder was very explosive so you would not want to actually store it in your home, and guns were very basic, where it would take a minute just to reload it after shooting. If someone were to break into your house at the time, you would not use a gun as first means of defence.

As times went by, however, the social norms around gun ownership have changed and the focus on self-defence have become more prevalent, to the point where the Supreme Court justices are now interpreting the second amendment in a way in which it was perhaps not intended.