Well, if it's not a real mission—if it's marketing bullshit—you'll never fool your own people. They'll see through that in a second.
Graham Weston has a worhwhile TEDx presentation[1] that presents a more complete thesis on this subject. He raises three criteria: employees want to be a significant part of a winning team on an inspiring mission.
Nobody feels good changing the world if their own contribution isn't significant. Nobody want's to work for a change-the-world startup that can't execute or stay solvent.
But mission matters, even to employees. It's why (as he mentions) the #1 employer of ivy league graduates has horrible pay and really tough working conditions: Teach For America.