@Destinyheroknight: @takashichea: Lots of them use different types of magic. If you look at the character pages on the Fairy Tail wiki, most characters have several types of magic listed. Usually, they just have a primary type they specialise in. Natsu's primary magic is Fire Dragon Slayer magic, but he also knows elements of Macao's fire magic (allows him to do more with his fire), he's somehow integrated Laxus' Lightning Dragon Slayer magic into his own (though he's only used it twice so far in the anime), and he even learned some transformation magic from Mirajane in a manga special, though I don't know if that's canon or not.
In terms of the Fairy Tail universe, I think they mostly specialise in one type because of two reasons:
- It takes years to learn and master one type of magic.
- You probably need to be exceptionally powerful to used multiple types easily (like, Makarov-level powerful).
I guess Hiro Mashima wants to limit his characters from getting overpowered. Plus, having one type of magic makes them unique a bit. Makes characters somewhat distinguishable to the fans.
Ultimately, these are the biggest reasons. Think about it this way, the members of Fairy Tail are like western comic book superheroes. Natsu has fire powers like the Human Torch, Gray has ice powers like Iceman, Elfman can transform into different creatures like Beast Boy. Sure, they would be more powerful with more powers, but not every character is a Superman, you know?
and they can still match the current people by just doubling there powers LOL!
Actually that's not really true. All unlocking their "second origin" really did was open up their "second" magic container, essentially increasing their stamina so they can fight longer. They might be able to use more magic at once that way, maybe making some spells more powerful, but it certainly didn't just "double" their powers.