Short answer: Because Google's going to beat them to it. (Oh calm down, Apple Faithful! I couldn't resist yanking your chain again after this week's earlier posting.) The long answer is a little more interesting anyway.
The rumor of the day is that Blackberry's parent company, Research In Motion, is working on a tablet that would come out in time for the holidays this year. Hmmm, I say.
If (Big "If") it is true, here's why this is a big so-what for Apple:
1. The Blackberry tablet isn't actually a Blackberry. It's a Blackberry accessory. To be more accurate; it's a "companion device". What this means is that there's no cellular networking on board. It 's meant to be tethered to your smartphone (Blackberry smartphone, that is).
2. See number one. This is enough to make it a non-starter in the game.
I will add this to the discussion. It was a month ago that RIM announced it is buying up QNX Software Systems from Harman International. QNX is the touchscreen software Harman uses in its "infotainment systems" in cars. Touchscreen. Hmm...
P.S. What's easier than stirring up Apple fans? Answer: nothing (although crashing a Windows system comes close).