I can easily see why institutioens would do this; the quota on my university e-mail is so low that it overflows every time someone sends a sizeable attachment. So I have had to go to other emails.
Moreover, in many institutions of education issues of “security” and “privacy” are taken to such extremes that blogs (with comments) and wikis are impossible to handle on the edu infra. The result again: outsourcing, using whatever is available. This might mean that edu institutions will miss a big part of the 2.0, p2p, social media - take your pick - revolution happening right now. Not good.