Why do people expect to be bowed down to for their birthdays?

Just wondering why people take the pointlessness if birthdays so seriously and selfishly? It's one thing to buy a person a present out of respect and friendliness, but it seems to distort peoples thinking into that of becoming a King/Queen. Most seem to expect too much, practically expecting to be bowed down to for the day or weekend almost like they've changed the World for the better, it gets so bad. Why? Just because they were born on a day thousands of others were? Makes no sense to me... Plus there's the people who go around inviting everybody they know to some expensive place just to expect the attendees to pay for the thing. Hahaha OK, you nobody, no problem.