I wonder if this is because they blatantly lie to their students and don't give them refunds:

https://udacity.zendesk.com/hc/en-us/articles/207991863-How-...

> Udacity’s content remains available once it has launched. Once online, our programs are maintained to keep the content up to date and optimized for your learning.

But this is a lie. You lose access to content after a course "ends", whether you've finished it or not. They don't tell you this until about halfway through a course, when it's already too late for a refund. Their support doesn't seem to give a shit, they just shame you for not completing the course on time.

The whole point of a MOOC is to do things at your own pace, and they encourage you to do so, so long as you're willing to continually pay to access the content of course. The one-time course fee only gives you access to the content for the duration of the course. You want to do self-pace? Great, now pay another $600 to continue to access it for another few months at a time.