Every good manager realizes that spending time celebrating is as important as spending time working. If you don’t stop to take stock of your successes, it’s hard to feel like your work is worth anything. When things go right, you need to honor it, that way you have a reason to keep working hard. Humans are simple animals, we need a little treat every now and again, just like our dogs. 

This is even true when someone is moving on to another job. If they were a respected part of their community, which hopefully they were, it’s the polite thing to do to give them a little going-away salute. You want them to leave with good memories of the company, after all. Who knows where their path will take them, and if you’ll need them again someday? Plus, it makes everyone feel good. And we spend so much time at our jobs anyway that it’s good to take a cake break every now and again.