You're basically saying, "there are consequences to action," which is still the same strawman from earlier. Nobody is arguing that there shouldn't be consequences to the PCs' actions.
The fact that actions in RPGs have consequences in no way justifies the Paladin's specific weird list of behavioral restrictions and the consequences for transgression. You're not in any way providing any argument that the Paladin's falling mechanics deserve to exist; you're pre-supposing that they exist and then saying, "well of course if you break those vows, bad stuff happens!"
You're putting the cart before the horse.
I see it as putting the fiction first, and then making the mechanics to match that. That is, in the fiction, I like that any Paladin that steps off the path loses his powers. To make that match mechanically, we give him a path, and we say "if you step off of this, you lose your Paladin powers."
Sure, you don't have to do it this way when designing the class. But, if the world you want includes "step off this path and lose these powers," then you need a "fall" mechanic. Carrots for staying on the path (fate tokens, divine tokens, whatever) aren't good enough, because you don't lose your powers, and thus the mechanics are not accurately reflecting the fiction.
Now, there's a good debate as to who dictates when the "fall" kicks in, but sometimes it should be obvious, and the GM should have the final say, in my opinion (as with all things). For instance, if the Paladin kills a Good shopkeeper in cold blood to take his stuff without paying for it, and the player says "no, I don't fall," we have a problem with the class living up to how it is fictionally supposed to function. Thus, the GM should be able to say "um, no, you committed blatant murder so you could steal. You lose your powers." Again, in my opinion.
Personally, I know there's a big movement for the carrot rather than the stick, but I like using both. They're both appropriate tools in RPG design at different times (like fail forward and, you know, just failure). And, if the fiction calls for "stick", then go stick.
Is a "fall" mechanic absolutely necessary? Well, for the Paladin that I want to play, absolutely. For many (most?) others? Not so much, and I get that. I'm not sure how they're going to resolve it in 5e, but I think it's not a strawman at all to say "the fiction works this way, so we make mechanics match, and following consequences from actions can determine a fall." Just my thoughts, though. As always, play what you like
