It might be that you'd like to finish drying out the wick so it doesn't mold? And use up the last of the water?

I seem to recall Technology Connections also complaining about the auto shutoff in his videos...

Why? Evaporation humidifier won't make more noise when they're empty, and water level detection is surprisingly hard to make reliable while still being convenient in consumer devices. And you have to refill them daily anyway, so using it as an 'empty' indicator doesn't really add much (in theory it does, but not in real use). At best one could say it's the energy savings, but for a device that requires daily maintenance (refills) I'm not sure if the benefits outweight the advantages.

For this type of humidifier you actually want the fan to run after the tank is empty so that the wick dries out. Otherwise you have a wet lump of filter just sitting in an enclosure growing mold and bacteria and gross.