When I was looking at home automation systems and all the insanity found there. at one point I said "if I were to design a home automation system from scratch what would it look like?" my answer for the physical layer was poe and managed switches.
As somebody that's looked into this... yes, but. The contemporary light switch is instant. Within a few nanoseconds of your brain feeling the "click", you see the light. There's a noticeable latency from an API request to the switch's control plane which then talks to the power control which then turns power to the port off and then the light goes out. You have the additional delay of poe negotiation for the "turn on" operation, too.
Which is still ‘instant’, but with some non-ridiculous implementation, also easy to do with a ‘smart home’.
Of course most implementations are pretty ridiculous, so there does that idea.
If you bumped that to 125 to 150W then it would yes be great for residential for all the reasons you can think of.
Cheap cable, crimp connectors. No license required to install.
Low voltage and generally much safer than 120V and especially 240V. Consider with power negotiation a default max power of a few watts which isn't going to start fires.
Wanna replace a light fixture? Unscrew the old one, unplug it. Plug the new one in and screw it back on.
Also imagine kid safe outlets that are standard world wide.
There is a good opportunity for a startup IMHO.
With 100W PoE, one can daisy-chain 10 light bulbs on one cable (or put them on different pairs of wires within one cat6 cable).
But what I really wanted is controllable devices, so that I could re-assign lights<->switches in my home hub.
UPDATE: and you don't need an electrician license to work with low voltage.