I have a manual thermostat, no batteries required. It has worked flawlessly for over 30 years. It has a simple intuitive interface: a switch for "heat" or "cool" and a dial with a pointer to set the desired temperature. Why make things more complicated than they need to be?
1. Economic - it easily paid for itself in one summer by not running the A/C when no one is home. I have geofencing set up to do this automatically.
2. Comfort - my office/bedroom temperature is all I really care about as it's where I spend all my time. My thermostat was not wired to there, and temperatures fluctuated wildly in my office. Ecobee has remote sensors so that I can set the rooms I care about to the correct temperature.
Overall, it has certainly made my life a lot less complicated; I never have to touch the thermostat again to get comfortable in my office, and I save a lot of money too.