In rural Vermont, which is clearly not where most people live, we lose power for hours or days (or even weeks) every year. I imagine there are many communities throughout the world with similar types of power interruptions. Anything that is "mission critical" for survival (heat, water, and the ability to enter our home) must be as reliable and robust as possible. The idea of replacing the perfectly functional metal-key technology, for example, with some door-lock device that depended on a temperamental electrical grid would be a strategically unwise decision. Big risks, little rewards. What is the fail-safe plan for these sorts of smart home devices when there's an earthquake or hurricane or something?

It should be totally possible to run a door-lock controller with minimal power consumption to make it last months on a relatively small battery without constant connection to the grid. You could even harvest energy from the door knob to make it completely independent from external power.

Of course the average "smart" lock is unlikely to be engineered with such considerations in mind and I doubt that the extra effort would pay off financially, but it isn't completely impossible.

The combination locks on individual rack cabinets at a data center I used to visit frequently were powered by the rotation of the front dial. Basically, you twisted the dial back and forth several times to charge it up, then pressed the buttons on the keypad, and a green LED lit and the bar retracted (or else a red LED lit and nothing happened).

This allowed them to (a) not run a power wire to every door; (b) use a long (12 digits) passcode; (c) reprogram passcodes in a few seconds; (d) immediately give feedback on whether you had typed in the right code or not.

IIRC they cost upwards of $500 each. Given that there was already a 24/7 human guard to check you in and out, I'm not sure that they made a smart decision over physical metal keys.

Meanwhile, I have a non-networked, non-wireless electronic combo lock on the front door of my house. It's not hackable without physical contact; if you want to break in, smashing a window is a better route. It's powered by a 9-volt battery and lasts about 4 years per battery.

The big win is never forgetting to carry a key, with a smaller bonus of being able to give friends individually revocable passcodes.

Agree.

Personally I don't see much use in smart locks for my home, but if I did have one I imagine I'd still use a regular key and carry it with me all the time. The smart lock could still provide benefits such as allowing visiting friends to enter without key etc.

Being able to remotely control and monitor the heat and water is awesome for the vacation house, but that is only in addition to using the physical knobs. It should not increase the risk (but in practice the security in such devices are terrible and you need to be somewhat knowledgeable to even assess the risk introduced).

How big is the current Spotify library (TBs, I assume)?