Guns and ammo are one thing. Folks realize the guns are xxx effective at yyy range, and so on.
Fuel is subjective. Highly so.
100 gallons on a 109 might give you twice the range as 100 gallons in a la7, and the la7 might fly 3x as longer as the 109 at 30k, simply because its power curve gives it so little power it uses so little fuel.
Gallons/fuel amount doesn't really help as a solid number. You'd STILL have to remember every plane's capabilities.
262 is a gas hog until you get past 15k. At 20k you get nearly twice the range because fuel consumption is half as much (the engines are at their peak efficiency at that alt). The Ta152 can list 50 minutes full throttle until you hit WEP then it says 35 minutes. The GPH jumps horribly when using WEP in that plane. So knowing how many gallons you have is useless without a large, comprehensive, mind-boggling, list of altitudes, GPH consumption, cross-listed with throttle and MAP settings, cross listed with many other factors.
Too much to keep track of. E6B is really a nice and easy way to figure it out. Quite handy, IMO.