I am not aware of many distros shipping the original vi today. However, a lot of them ship busybox, which is a self-contained and lightweight collection of standard UNIX tools, including a simplified vi. If you have a UNIX shell on an embedded system, there is a good chance it is running busybox.

vim is an order of magnitude bigger than the entire busybox package. In fact, it may be bigger than the entire system.

Including Vi-improved would be complicit in the assumption there was an imperfection in vi.

To save precious disk space