I think that credentials and requirements are indeed wanted by many students, but not by all of them. If you already have a degree from a university, and you take some MOOCs for fun, why would you bother with it?

In my case, I have my degree in compsci, but later realised I do have an interest in philosophy as well. Due to working I could not go study the full-time course, but my uni offered me to study philo at my own pace (each semester, just take courses a,b, whatever). Without having a degree at the end of this.

To conclude, I believe some students do MOOCs purely out of interest, and don't attach as much value to the certificate because of that.