You know, aside from the benefit of prophylactic protection from CV, and making a point about the safety of the medication... I'd guess the whole "...relish the reaction..." might be 50% (or more) of the reason he's doing it.
President Trump personifies "living rent free" in someone else's head.
He owns the leftist media. He knows it, they know it, and there is not a damn thing they can do about it. They have to do the things that they do - it defines them.
Being predictable puts you at the mercy of your opponent, and the leftist MSM is entirely predictable within very small confines.
There is probably some significant positive news about to break on the efficacy of the medication. President Trump lets it be known he is taking it - MSM predictably goes ape...bam, news drops and the left looks like horses' backsides, again...
Easy to do because they ARE horses' backsides!!