Since it has 1 HP, what is the point in Shedinja having Defense and Sp. Defense?
What's the point of giving Pokemon SAtk when its Physical Attack is much better? To fill a void. Sure it has 1 HP, but the same can be said to giving Shuckle Attacking Moves or Blissey Defense. If Shedinja had no Defenses, it'd be no different than if it did anyways. This could be Gamefreak's way of trolling as well. If a Pokemon were to have 0 Defense, that would very much glitch the game every time it gets hit in battle, as not damage can be set really.
well, actually theres no point at all. but it would be even stranger if he didn't . like, no Pokemon can have 0 in any stat, so its simply just to don't have it
Actually both of you forgot something. These defenses would be taken into account when it's behind a Substitute. How does it get behind a substitute you ask? Baton Pass.
Step #1 Any Baton passer with Substitute and any defense boosting move.
Step #2 Baton pass a substitute and maybe a few defense boosts (your choice) and set up a few times if you want and you have Death. I recommend Drifblim to Baton pass because it has access to Stockpile.
Hope I helped! -demat
It's a late reply but one reason I can think of is when someone uses Guard Swap on Shedinja. Guard Swap switches the Defense and Special Defense stats of the user with the target's, but I'm not quite sure why anyone will want to do that considering Shedinja's below mediocre 45 Def and 30 SDef stats. And of course, like the other answers have mentioned, to fill in the void, increase Shedinja's low base stat total, and also the Substitute strategy.