the universal gift

What makes a mug the one neutral gift that is acceptable to give in almost any situation? Come on, how many times have you received a mug as a gift? In both my social work placements, my supervisors gave me mugs at the end of my term with them. Case in point:

Currently found in the communal cupboard of the home kitchen.

I guess a mug transcends culture without the risk of offense or cultural inappropriateness. But to be honest, I would've appreciated a couple of unmarked bills in a sealed white envelope.

If anyone who ever plans to give me a gift is reading this post, you know what to do.