Box office nerds speculate a few reasons for why sales were so bad this year, which includes the World Cup, bad weather, and the most likely reason, there wasn't anything good playing. Per BuzzFeed, this weekend's box office "was the lowest grossing 4th of July weekend since the 1980s, when adjusting for inflation:"
Because July 4 falls on different days of the week each year, it's difficult to make direct box office comparisons for Independence Day weekend: July 4 fell on a Friday this year versus a Thursday last year, for example, meaning many adults had just one day off in 2014 versus two in 2013. Still, Transformers: Age of Extinction dropping 63.6% from its debut weekend, with just $36.4 million over the holiday weekend, does not bode well for the long-term health of the franchise. In fact, it is currently tracking well behind the domestic grosses of the first three Transformers films.