What do you mean by "What benefit does it bring"? It's a consequence for breaking your oath. I appreciate that you want to play an oathbreaker, which isn't really the intended play style and so it's not properly supported: perhaps it would be better if you could select that as a subclass when you create the character, so you've never had an oath (in game) and therefore don't have to pay to respec. But, in the system as designed, breaking your oath is supposed to be a penalty (disclaimer: I have never played Paladin myself, and I know there are plenty of complaints about the game declaring an oath broken when the player disagrees).
Asking what benefit the consequences have is like asking why vendors charge money for items, or why characters can die in combat. Sure, it's not fun when you have a TPK, or can't afford something you need, but the game overall would be less fun if there was no challenge in it.
To summarise, you're choosing to play in a way that's not in the design, but it's supposed to be a consequence of failing at another form of play. That's why there's a penalty built in.
