They do ... we get specific doodles for specific Brit high days. Last week or so ago, it was some geezer who invented the holgram's turn. They do global events too... it's all FIFA World Cup at the moment.
Google ignores a lot of American "high days". We mostly get birthdays for people who are already dead and celebrations of various foreigners in the arts. :(
The huge number of global/non-American references made me think that all English-speaking users got the same slate of "holidays".