A lot of guys are complaining in the thread, with undertones of an expectation of sex
Most likely reason I see that would cause this data: the immense social pressure applied to straight women has lessened in the 21st century. A straight woman won't be ostricized at 25 if they don't "have a man." The data suggests that young straight men aren't having as much sex. I postulate that the only reason is that straight men need to work harder to impress empowered straight women. And that the overwhelming majority aren't even trying.
Most likely reason I see that would cause this data: the immense social pressure applied to straight women has lessened in the 21st century. A straight woman won't be ostricized at 25 if they don't "have a man." The data suggests that young straight men aren't having as much sex. I postulate that the only reason is that straight men need to work harder to impress empowered straight women. And that the overwhelming majority aren't even trying.