They've sold about a million RIM Playbook devices so far. Apple sold 37 million iPhones in 2011 Q4 alone, and 11.5 million iPads in the same quarter.
Building software for the Playbook would cost ... I'll just guess at a very low $50K in development and ongoing support and maintenance costs. The iPad is $499?
Let's suppose there are 100 would be owners of the BDP-1 who would also buy a RIM Playbook. It would be less money to buy them all new iPads than it would cost to make a new app for the Playbook.
Not really my place to comment, but that's the uphill battle RIM is facing as they decided to invent a new platform rather than pick something like Android. Theirs is a path fraught with peril. And I'll be super impressed if they can pull off a second act.