People are volcanoes, lust is their magma.
Hot volcanoes (hot people) get to vent their magma with someone else, who is also usually hot.
Those who are less hot do not get this opportunity, and the magma builds.
They have to vent themselves to release this magma.
If they do not vent (through masturbation) their magma (lust), the pressure (sexual frustration) builds and builds, until they blast away everything before them in a vicious pyroclasm of despair (rape, paedophilia, murder). [Note to all: Extreme Case Scenario]
Vent regularly, and your magma is safe.
Masturbate regulary, and your lust will be satisfied.