Their development roadmap could easily change after the acquisition. More importantly, Microsoft already has plenty of people who have a lot of experience addin

Their development roadmap could easily change after the acquisition. More importantly, Microsoft already has plenty of people who have a lot of experience adding enterprise features to products. It makes far more sense for them to buy the calendar company that is best at the things they don't have, rather than the one that has more of the features they can straightforwardly add.