You know, as a kid who bought a lot of cheap used cars and still today I buy cheap old cars; I was told and believe that a car with a temp gauge is more likely to be the better car.
If a car is running hotter than usual, it is likely to be bought in for servicing.
With an idiot light, there is little warning before the engine just burns out.
I think a used car without a temp guage should be knocked down a few hundred bucks for having "unknown wear".