Chavez is from the left-wing military tradition of latin america.
(Which has a great deal of credibility, generally seen as being removed from party politics and leading the fight for national independence/honor/wealth. Of course, the right-wing military tradition has all of the same percieved attributes.)

He's clearly been taking some cues from castro in being flamboyant and dramatic. (see castro's "we who are about to die salute you" speech.)
And why not? It's popular, serves to draw the battle lines, and is frequently amusing. Of course, he'll still sell us his oil so we can keep our society going and we'll still buy his oil so he can keep his society going.