TP was a resource that was unnecessary. I spam the mess out of weapon skills and my TP always stayed high. You would NEVER run out of it, essentially making it useless.

MP, though, is a whole different story. The whole point of being able to use magic in this game or any other game, is that you have to have mana to do so. If you don't have the mana, you don't get to cast your magic.

Think of it like Magic: the Gathering. Does it cost mana to attack? No, unless the defending player has a buff up that forces you to (similar to attacking into something in this game that drains your health). Now, if you cast a spell, can you do it for free? Not usually unless you have a combo out. You always have to use mana or some other resource to cast spells. Using resource to just swing your sword and go pewpew has never been a successful thing.