How come I would sometimes get the prodrome symptoms of oral herpes but never the actual blister?

Immunity. The varying degrees of immune mechanisms which keep herpes simplex virus in check are not fully understood. We know that some people are prone to frequent outbreaks and others have none, and some, like you, get only partial symptoms. Consider yourself fortunate.
Better . It is better to get the prodrome rather than the actual blister as that means that the healing process would only be a fraction of the time of the blister. If the prodrome reverses for any reason, then the blisters do not come about.