The simplest examples I can think of would be:

• you meant to before you left but forgot
• weather conditions changed so your house temperature needs changed
• you want the house to be warm or cool when you get home, similar to the main benefit of remotely starting a car

I know many dumb thermostats support scheduling, which might preempt the last one, but if - again - you forgot to set that up or you didn't know when you were going to be home, it would be a boon to have a way to address that.

Also, most of the smart thermostats I've seen have temperature threshold alarms. If a fire starts, you would get a notification and hopefully be able to do something about it. Or if the climate control system fails while you're out, you can respond as appropriate.

I agree that there is no biological imperative for smart home equipment, but I have appreciated mine many times; and I mostly self host, so in theory I'm not giving away data. To me, the only downside is the cost, which comparatively isn't really all that bad in many cases.

For the pets, or preheating your home for when you're there.

I could see the reason for scheduling a thermostat, at least. Mostly to save money on heating/cooling when you are not home.

One reason we like the remote thermostat is it allows us to adjust the temp automatically for house plants depending on temp and humidity.

To save money on your electric bill. A smart thermostat will know when you're not home, and automatically turn up the temperature to keep the bills down. It can also know when you're heading home, so that it can turn it back down and have the house already cooled for you before you even open the front door.

You can also use them to automatically pre-cool your house at night, when electricity is cheaper. The residual coolness keeps temperatures down and the thermostat doesn't have to run the A/C as much during the day, when electricity is more expensive