In the good old days a jet didn't climb out under 300kts. It was published in our books. Then the accountants told the company to tell the pilots to climb at 'econ' speed or 'cost index' speed (whatever any of that means?). Nobody told the ATC's, got a few 'surprises' when it first started happening. Asking the pilot in front to climb not below 300kts fixed it.
Any inquiry conducted into these incidents wont give the real reason why these BOS's are happening with monotonous regularity. I can tell you some of the reasons, it started you know where, when someone who trained bank tellers believed that 'anybody' could do ATC. By the same premise, that means that 'anybody' could be a doctor.........right? Anybody could fly an FA18 mission into Iraq............right? Anybody could be a trapeze artist?