If clubs, daggers, and quarterstaves are just as good, why did anyone bother inventing the sword and the battleaxe?
Because they are only good for a small corner case of people.
If you aren't a rogue, you probably want something better than a dagger. If you aren't a battle templar using these specific powers, you may want something better than a greatclub.
However, for a small number, there is a preference.
Barbarians like big weapons (for the most part). An Avenger wants to wield a two-handed weapon since they can't benefit from shields. A warlord or warpriest get shield prof, so they'll probably pick a 1-handed weapon, while a battle templar, lacking shield proficiency, might as well get a two-handed weapon. Slayers likes axes and swords, while a knight likes hammers and swords. You
could have an axe wielding knight, but he misses out on bonuses. You
could have a longsword/broadsword wielding rogue, or a hammer wielding dwarven rogue (with feats), but they aren't as good as the real thing (in the case of thieves, the bonuses they give to light blades makes any replacement weapon inferior).
Each class is given an implied or forced weapon selection based on proficiencies. True, anyone could just grab shield profs, weapon profs, armor profs, etc but there is a sort of style being assigned to each class based on their initial proficiencies. Sometimes, this is reinforced by things like rewards for playing "in style" (The tempest or battlerager fighter going with chain or light armor; primal classes in light armor; monk, avenger or vampire in cloth armor; knight using sword/hammer and shield; sentinel druids favored weapons) or are reinforced by restrictions (sneak attack damage restriction; tempest fighter powers; most ranger melee or beast powers; etc).
There isn't really a class that favors simple weapons (the sentinel druid and rogue, sort of, but those are only a few of them). This is a sub-build or a battle templar, which is half of the templar, which is one of two builds for the cleric. So it's one way to build 1 of 3 clerics. It's also only one of many strength based leaders. And even with the powers, half of them are still fine for use with any weapon you want to bring into the fight.
Weapon Prof is already nearly a feat tax for most weapon wielding classes ... it's nice to have a few clases that don't use implements that actually are happy to use their normal weapon proficiencies.