I think it's because fuel tank sensors frequently break, due to being buffeted by sloshing fuel, and sometimes getting corroded if there is a little salt water in the fuel, so car manufacturers have decided to use other methods other than a float and variable resistor...

I'm not sure what is actually used instead, but I'd guess they just measure the pressure on the inlet to the fuel pump. An absolute pressure sensor only costs 3 cents and the fuel pump is probably already on the CAN bus.

Back in my day, before all the newfangled shiny sensors you would get an accurate fuel tank reading every time - except if you were going around corners, accelerating or breaking, or had done any of those in the past few minutes and the spring returning the float was feeling slow that day.

Otherwise it was, like all things back in the good old days, incredibly precise +/- 10%

"Otherwise it was, like all things back in the good old days, incredibly precise +/- 10%"

The sad thing is, if todays values are worse.

My first car the sensor was clearly at the back of the tank.

Going uphill? Gauge says 1/4 tank left.

Steep downhill? Out of gas.

Not sure which end the pump was on, but I never ran out despite what the gauge would say.

Ahh yes, how could I forget about the hills, you are giving me flashbacks to the good old days!