That would be a bad idea.
1. A default password is a default password, and should be assumed to be public knowledge.
2. A complicated default password will accidentally trick user into thinking it is more secure than admin/1234. For example, you have already been tricked.
3. If the device is reset to factory default, the password won't be easily remembered, so a device may be stranded in a default or even unusable state until the owner can find the password via documentation, help-desk, or internet database of default passwords.
A partial fix that is sometimes used, is to give each individual device a separate password, and include this password inside the packaging or attached via sticker. This is somewhat more secure but can lead to problems itself. The user may keep the password, and the password may not be truly unique, or may be guessable. If the password is damaged/lost, the device may be rendered unusable if reset to its default state.