Blackberry phones just seemed to become 'cool' for a period. I don't think 'email' was ever the reason.
I remember almost every American TV sitcom and movie would mention the name "Blackberry" instead of "cell phone" in their shows. I'm not sure if that was through paid advertisement or just writers jumping on the bandwagon.
But 'cool' doesn't last long for a product. Remember the Tamagotchi? Boom and bust within a year.
Apple rule the planet. And there is nothing we can do about it.
The Blackberry OS wasn't written from scratch by RIM.
RIM bought QNX Software Systems because QNX Neutrino is a mature, elegant, and efficient RTOS. I have taught a college RTOS course using QNX for about 10 years. iOS pales by comparison.
Apple is grabbing those enterprise slots pretty fast. In addition many enterprise adopted BYOD(bring your own device) policy at work. So to say "Blackberry is still, and will always be" is very optimistic.
For every Blackberry owner I ever knew, "email" was precisely the reason they loved it so much. But for ordinary web browsing, it was pretty lame.
And as eewiz points out below, even RIM's traditional preference as the corporate phone is becoming less relevant as more and more companies adopt BYOD policies.