Apple or Microsoft could easily compete more evenly with Blackboard if they wanted to, but they choose not to enter a lucrative market.
If you examine the market caps of the three companies (Blackboard, Microsoft, and Apple) you'll see that Blackboard isn't even a blip on the radar of the other two. To Microsoft and Apple, the LMS is not a lucrative market. In fact, I asked someone in the LMS industry recently why there wasn't any SEC scrutiny of the ANGEL/Blackboard merger/acquisition. His answer - it's too small a deal!