I don't know if that's really based on the way implements work vs how weapons work. I think it has more to do with the "shtick" of the Warlock, which is that it has a lot more controller-like features then the other two Strikers, and which probably lead to an intentional reduction of damage values.
I think the "easiest" thing to do for WotC would have been to make Implements just a kind of magical weapon. Games like Diablo already did this, IIRC - Staves, Rods and Wands in Diablo II for example gave you a basic attack you could use while not using any of your powers, just like Swords, Axes and so on did it for non-magical attacks.
I wonder if they didn't do it this way because they wanted to avoid further "video-gamey"-screaming or something like that. But there is an alternative possibility- they didn't do it because balancing powers around damage proscribed by the implement you use gives you less flexibility. You can not only change the number of dice rolled, you can also change the type of dice rolled when using a certain power, and you can also change the range.
But I could see a system where Wands, Staffs, Orbs and Rods gain fixed damage types.
Maybe Wands and Rods are "simple" magical implements. Wands deal 1d6 damage and have a range of 20. Rods deal 1d8 points of damage and have a range of 10.
Holy Symbols, Staffs and Orbs are "advanced" magical implements.
Holy Symbols deal 1d8 damage, have a Range of 5 and do not require you to wield them in your hand.
Staffs deal 1d10 damage and have a Range of 10.
Orbs deal 1d8 damage, have a Range of 20 and add +1 to the area of your blast and burst effects.
Instead of setting fixed ranges, you could also make it range modifiers +0 for Holy Symbols and Rods, +5 for Staffs and Orbs, +10 for Wands
If you'd wanted, you could also add "proficiency" bonuses for each implement. (Wands +3, Staffs +2 and Rods +2, Orbs and Holy Symbols +1)
A spell like Fireball would deal 3 damage. (I standing for Implement damage).
I wouldn't be surprised if some draft for implements used similar ideas.