Question about flamethrowers

Thunderclap

Many flamethrowers use compressed flammable gas, which flows from the special tank to the end of the gun, where it is ignited by spark plugs. This creates a small flame, which ignites the flowing fuel.

But why a flamethrower needs a tank with compressed gas? Can the fuel be ignited just only by spark plugs?

NascentOxygen

Have you tried lighting a kitchen gas stove ring? I know modern stoves have automatic electric ignition, but the older ones require that you use a match or a gas igniter. The gas igniter is like a butane cigarette lighter but with a long barrel. When the butane runs out you can still light the stove, but it is unreliable and you often have to make many clicks (sparks) before ignition. When you recharge the butane, ignition is usually on the first try.

I'd say the butane provides a fuel-rich mixture so it ignites easily; the gas stove is set to provide no excess of gas for maximum heat and smoke-free operation.

SteamKing

The compressed gas also projects the flame so that the operator does not roast himself.