What purpose do mock os serve?

For the life of me I can't think of a practical purpose to all the mock os's out there. What are they used for? What do they do? Why?

Well, a lot of Mock OS's have very little purpose. However some do useful things such as file management, having useful apps (like a calendar), etc. My philosophy on Mock OS's is that it's really only good if it can actually run similar to an actual OS or be expandable. Otherwise you'd get a file manager, a calendar, etc. Most that I've noticed do not fall into that category and are really lackluster (they can get good when they have a lot of features though).

I honestly have no idea at all. Most of them are simple text input/output programs I believe.

It was an old fad back from the days of Petit Computer, where kids people who couldn't think of an original program idea simply tried to one-up each other in the game of making THE BEST OS. The end result was a lot of petty insults, relatively useless programs flooding the activity, and mildly upset 13 year olds... wait... (In my opinion) Unfortunately, it carried over to SmileBASIC. I'd say they improved in quality in the transition, but it's still not very helpful.