Now I find this interesting. Personally, with my playstyle I get better (or really, more desperate and/or serious) when I get backed into a corner. So, when I'm low on hp and finally trying my hardest, I can really put up a fight (and even come back and win), but the fact that anything more than a cherry tap will KO me really snuffs out my potential (that, and by this point the other person usually can win by scratch damage even if I block). Enter X-factor. Gives the boost people like me need to make that comeback a reality.
It's like an adrenaline rush, it gives you that extra edge. Plus it's balanced because the attacker can use it too, so it's not broken.
It's not luck if you outmaneuver your opponent to grab the smash ball, it's skill.... with a little luck thrown in. It's fundamentally the same, because even if you're in the upper hundreds, if you land a final smash you are likely to take a stock. Like an offensive comeback.
Naturally all of the above is my humble, casual-playing opinion.