Before the age of computers and emissions of vehicles you could run lower temperature thermostats without hurting anything but the heater output.

Today the engine temps run hotter for better emissions and the computer is programed to monitor the thermostats performance and report with the check engine light if it's not correct.

I often wonder if the engineers disable the coolant temp gauge when there is a low temp fault to promote people to fix the problem instead of just diving around with the check engine light on knowing its a low temp fault and not fixing it.