You can't export or import your code there, you can only type it in. (Unless something's changed lately.) Even micros in the 70s could save/load cassette tape.
(Codea is pretty neat anyway. I get sad to see the potential locked up.)
If we're talking about getting a kids to learn how to use these wonderful tools, that's a feature, not a bug. I for one know that I learned to program precisely because I couldn't just swap cassettes with the other kids. I had a crappy computer that no one else had, so the only games I had were the ones I typed in myself. That act of typing (and hence reading) the source code was how I learned to program.
This is neither a feature nor a bug. It's a restriction forced by Apple.