There are a few things with Emerald in particular that could be affecting your chances.
First, Emerald was the first game to implement Synchronize’s secondary effect; if you don’t know, in every game since Emerald, if a Pokémon leading the party has the ability Synchronize, all wild Pokémon have a 50% chance of having the same nature as the Synchronizer, so if you’re leading with an Abra or Ralts, that could be the reason.
Secondly, Emerald’s Random Number Generator is glitched to have a fixed seed. What that means is that, every time you start the game, it will reroll the exact same numbers on the exact same frames, so the fact that you’re SRing doesn’t do you any favors. That being said, if you’re not accidentally using a Synchronizer, then I don’t know what to tell you; you’re just getting super unlucky. However, if you are Synching, then you’ve probably been hitting the exact same two or three modest Aron several times in a row without realizing it.