I never understood the smart lock. Some other connected appliances make sense - HVAC for example. But unlocking my door with a key is such a trivially easy, failure-proof thing to do, and every smart lock I've ever seen so riddled with failure modes, that it boggles my mind anyone would go through the cost and effort to install.
I've had a key break in a deadbolt lock before. I can go running without carrying keys. I can assign a temp code to my pet sitter/handyman/whoever without having to police up keys or worry about keys being copied. I know when and which code is used, in case of an incident (none so far). My partner has lost 3 mailbox keys and zero house keys (since there is no house key). My door auto locks, and forgetting to lock your door is one of the biggest security risks, since crimes of opportunity are so much more common than targeted crimes. I've given my neighbor access during an emergency while we were out of the country. I can pre unlock my door from my smart watch if my hands are going to be full. I absolutely think the cost and effort were worth it for me.
But, the obvious failure mode: you assume it locked automatically behind you, but how can you be guaranteed of this without checking? It seems to me at that point it's better to just lock it with a key, which guarantees it's locked.
I get a notification when the doors lock. I can also check the status of the lock in Home Assistant.
If for some reason the deadbolt jams, or the door was not actually locked, then I risk it for those few hours. It hasn't happened yet.
I have probably "manually" forgotten to lock my door more times than that. (e.g. Carrying items out to the car, I think I will go back for more, then I get distracted and leave instead.)
I like my auto lock feature, but I manually lock it as a habit and only rely on the auto lock as a backup in case I forget. I only have to touch the keypad to lock it and can hear it lock. Also, I can check remotely if it is locked (even though the lock can/does work completely without a need for a connection).
