It's a series of probabilities; much of the time, you can install whatever editor you want, but vi being included in ex. busybox means that there are places whe

It's a series of probabilities; much of the time, you can install whatever editor you want, but vi being included in ex. busybox means that there are places where it's really nice to be able to use vi because it's there by default and installing something else would be inconvenient. For example, every Alpine Linux container has vi, as does the OpenWRT base system.