I have a question I guess about architectural history. I recently purchased a home built around 1915.

One thing I've noticed is that every single interior door has one of the old-style mortoise locks with a deadbolt. Even every closet has one. I'm assuming this was a common thing back in the day (I'm hoping I'm not living in a former prison-house).

My question is why were these locks used so frequently on internal doors. Was safety really that much of a concern? Wikipedia makes it out that these were not easy locks to install. Just trying to learn more about my house's history.