What's With the Public Birthday Parties?

Why do people have to celebrate birthdays in public?  Have you ever been sitting at a restaurant sharing a nice meal with your family or friends, and all of a sudden the staff breaks out in the Happy Birthday song?  You have now been forced to become part of a birthday celebration of a complete stranger.  You have to interrupt your relaxing evening in order to share in the glee of someone's birthday that you have never met.  In my opinion, if you want to celebrate your birthday, do it at a private party in a private home and invite people that can decide yes or no if they want to attend your party.  People should not be forced to be a "guest" at public birthday parties.  That's all.