Because I don't think anything but the bursts (10k stars/manyshot) compares to the damage the caster side can do consistently as long as the blue-bar is still there. And then there's the blue-bar damage you can do when you really open up and go full-out with the nukes. Most builds I've seen account for the lack of big ranged damage between the bursts by supplementing with melee. I'm curious if you could bridge the gap between the bursts with casting instead and then have unbursted ranged damage as a fall-back to both. There are some fights (EE FoT for example) where there's so many hp's on the stuff you're killing that you'd love to have a decent non-sp option for damage on a spellcaster. Otherwise you end up potting all the time. Sure, you can do that...the question is whether you can build an option that gives enough ranged damage as to be worthwhile for those longer fights.