Your snowblower and lawn mower don’t have the weight of 10 gallons of gas pressing down on them. Our yard equipment all have shut off valves under there gas tanks just in case something were to happen.
Why do you think the manufactures put the shut off valves there?
Enjoy.
i have a to35 massey that has 8 gal. of fuel in a tank directly above the engine. it does not drip fuel out the carburetor.
the fuel shut off at the tank has another important use. it is there to shut the fuel off to the engine so you can fix your carburetor properly.
that is why i think it is there.
shutting that tank valve off is probably a good idea while the car is park for extended times. but, i would not trust it. they can leak too. so if that leaks and your carb leaks you have not solved any problems.
another thing
if that carb is leaking when the car is not running that means it is also leaking when the car is running. if it is dripping on the ground, you maybe ok with that but if it is leaking internally you will never make that engine run correctly.