Another reason to not ship Flash is that by the time you install the OS, the version of Flash is usually outdated and you've got to install the update anyways.

Another reason to not ship Flash is that by the time you install the OS, the version of Flash is usually outdated and you've got to install the update anyways. Every time I reinstall an OS, Mac or otherwise, I find myself having to update Flash. If I've got to do that, I may as well install from scratch.