Blackboard is shockingly awful, but the people who nominally control the purse strings in education are an incredibly cautious (cowardly) lot, and so for the most part they'll just buy whatever everybody else in their community does.

The teachers who are on-the-ground have very little say in the purchasing process; they're just handed tools and told to use them. Which is why Blackboard continues to have customers, in spite of their shockingly bad product.