As a mechanic...when I own a car, I want to be able to know what everything the car's doing all at one time. Especially gauges... I am trained to installed gauges into everything on what I work on and I have to properly diagnose a problem using gauges before i start tearing something apart and costing the customer tons of money that even I know I don't have. A temperature gauge in a car is a VERY important thing, but the gauges in the cars are almost as unpredictive as the warning lights. Chevrolet, for instance, has put temp and oil pressure gauges in vehicles for years that show temp and oil pressure, but unless you know what's "normal" is good to go. For instance the temp gauge on most chevys is 150 - 200- a hash for "about" 230 and overheat at 260... what does that mean to common people??? "Well, when I'm driving my car the needle points to the middle of the lines on the gauge, between the numbers..." THAT'S what people commonly call "normal", but in fact, it could be over heated or not...you have no way of really knowing, even with a gauge, because the manufacturer doesn't tell you what the engine's actual temperature is supposed to be stated "normal" in the owner's manual. Just like, commonly, the engine oil pressure isn't mentioned to what is normal even with the gauge installed either. People just know if the gauge doesn't move, that's bad, and if it sky-rockets. That's bad also. Ford's Gauges don't even have numbers on them!!! How in the heck does that work out????
Also, if you actually monitor engine behavior compared to an electric gauge signal...you might not notice a problem anyway. Most gauges aren't calibrated correctly anyway. I have a car at home that has a 3.1L GM engine in it, that the temp gauge on the dash is +40 on what the actual engine temp is. At 200 on the dash, my thermometer was showing 160 at the radiator and at the thermostat...
People get so used to everytime they get in their car to drive, it starts fine, it goes into the selected gear just fine, and runs fine so many more times than it has issues, that other than fuel and speed. They don't even look at the dash. So if something fails and light or gauge pegs out; they don't notice until it's too late already.
Sorry for the rant, just wanted to clear some stuff up.