Why /zip is read-only?

[franalbani]

For some reason, I was confident that it was possible for a cosmo binary to write inside /zip (and even persist the changes in the file itself).

But after failing to do it with cosmo's python:

$ ./python -c "open('/zip/memories.txt', 'w').write('memory')"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
OSError: [Errno 30] Read-only file system: '/zip/memories.txt'

and then verifying with a simple C example, I started git greping the repo searching for something to prove myself I was wrong.

This is the only thing I found:

// zipos being a read-only filesystem, ...

I would like to understand why it is so and if there is another way to achieve the same result.

Thanks!