Indeed; without a hat bent at the appropriate angle, it can be difficult to ensure that magic cast across a distance of air between you and your target will travel in the direction you want it to. Wizards have specially-enchanted pointed hats that 1) act as a focus to give magic a bearing relative to the angle of the hat and 2) ensure that the angled tip of the hat is always at the same angle relative to the caster's facing. Then, when the mage has become accustomed to accounting for the angle of the hat, he can successfully will his cast magic in the direction he so desires.
In short, the hat gives the magic direction, the mage provides a modifier to this direction in order to direct his or her power.
Other items can act as a similar focus, but the hat is an old tradition, and magic is often as steeped in tradition as the organization of military powers.
In order to focus magic's direction without the aid of an enchanted implement, a mage must concentrate much harder on the task at hand, which can be mentally exhaustive, but represents the transition from a mere novice to a well-adapted scholar of the magical arts. With more and more practice even that becomes as simple and instinctive to the mage as swordplay is to a masterful swordsman.
In terms of why so many magi choose to use simple elemental attacks; it is sometimes a lack of imagination on their part, that they cannot adapt to the idea of causing harm without invoking the special powers of nature, and yet sometimes it is also because these sorts of things most represent the power of a magi to the uneducated multitudes. A sort of shock and awe tactic.