Verizon just got the iPhone - why would they want to take a chance on the Bionic competing against iPhone sales, or take a chance on those that buy an iPhone bringing them back in 30 days to exchange once the Bionic comes out?
They're targeting completely different markets. That might be part of the reason, but it can't be the whole reason. I can't imaging someone clamoring for an iPhone on Verizon suddenly falling in love with this gigantic beast of a device instead. On the same note, I can't imagine super high powered corporate users needing state of the art dual core powerhouse phones with HDMI out, including 1080p mirroring, ever giving the iPhone more than a cursory glance.
iPhone's targets, specifically on Verizon:
1. Verizon users clamoring for an iPhone on their network
2. AT&T users clamoring for an iPhone NOT on their network
3. Potentially disgruntled android, blackberry or windows mobile users who continue to receive not only less selection of apps available for their phones, but also not having access to some high grade ones that continue to be only available in Apple's app store. Android continues to catch up, and many people say that Apple's advantage is merely a numerical one because of all the fart apps and such, but there are still major and popular titles that are a long way yet from coming to android. It will only get better, but some don't want to buy a nice phone now, and have to wait for their favorite apps to finally make it to their device.
Bionic's targets:
1. People upgrading from the Droid X, or perhaps one of the keyboarded droids who have become more comfortable with touch screens.
2. Business and working folk that need the HDMI out
3. Gamers - Tegra 2 does very well in gaming benchmarks, even though software still doesn't yet take proper advantage of dual core
4. Motorola's reputation for great signal strength, call quality, and battery life - the Bionic and Atrix are getting monster batteries.
5. And just anyone wanting a powerhouse phone
Totally different targets. One could also wonder why they're releasing the Thunderbolt this month too, and again the answer would be the same - totally different targets.