I think Cursing helps relieve stress in a verbal way. But then again, so does saying "Ow!"
Usually when I see people cursing, it's a result of mental or physical pain. In my experience, they don't say it unless they're angry, hurt, or freaked out... so when I hear "F-word" or "G-d word," what I hear is, "This hurts!" in a more aggressive, defiant tone.
Cursing makes people feel like they're acting rather than reacting, even when they really are just reacting to discomfort. That's the appeal, IMO.
And yes, they will often revert, because it's a more instinctive reaction than many other impulses. This is why Turret's Syndrome sufferers with Coprolalia find themselves cursing all the time. Something keeps triggering that instinctive response.