I'm not saying that penalties don't take skill, it's rather about what kind of skill they take. Your own examples are proof of this, Messi especially, as he's one of the greatest attacking players of all time, yet a mediocre penalty taker. It might as well be a different game and it says absolutely nothing about how good a player is a striker. On top of that most teams have several capable penalty takers, making the skill quite redundant, especially in Lewandowski's case as he actually misses the occasional penalty.. In terms of determining a striker's performance they are stat padding and I really hope some day they are tracked in a separate category. At least in the case of xG some of the providers actually do so already.