Comment by DerekL

Portability between different computers is only a secondary reason for the Z-machine. The most important reason is code size, making the largest possible game that can fit on a floppy disk.

See the article “How to Fit a Large Program Into a Small Machine” by Marc S. Blank and S. W. Galley, in the July 1980 issue of Creative Computing. https://archive.org/details/creativecomputing-1980-07/page/n...