After you fly your airplane for a while, you will learn how many gallons per hour your airplane burns in cruise and how much to allow for the first 10-15 minutes of climb to altitude.

There are also flow meters that will tell you how many gallons per hour your engine is burning. I have mine calibrated to read 1/2 gallon per hour MORE than I actually burn. Just my conservative nature.

Between the fuel meter and knowing my fuel burn at cruise, I personally do not see the need to have gages in the tank. It's just another system to be maintained.

Finally - with 28.5 gallons onboard (26 main and 2.5 in header tank) the airplane will fly a lot longer than I can.

Regards
Rodney