Create a node programmatically on installing a module
The problem is that install/uninstall and enable/disable are two separate things in Drupal.

When you enable or disable a module, hook_enable() and hook_disable() are invoked respectively.

When you install or uninstall a module, hook_install() and hook_uninstall() are invoked respectively.

If you want to keep your code in hook_install() / hook_uninstall() you'll need to disable the module, and then uninstall it at http://mysite.com/admin/modules/uninstall. Once you re-install it (which will also enable it), your code will be run.

It might be worth having a think if this code would be better served in hook_enable() / hook_disable(), but it will depend on your particular situation.