Tiger Woods is once again missing a major at this week's U.S. Open after undergoing his fourth back surgery in four years. This latest setback increases the number of rounds Tiger has missed (due to injury or missed cut) at the majors to 58 since turning pro, with 56 of those coming in the last ten years.
At the same age (41), Jack Nicklaus had missed a total of eight rounds in his career at the majors, and none due to injury. In fact, by the time Nicklaus won his 18th major at the age of 46, he only missed 15 rounds at majors with only three of those due to injury. Those came when he was 43 years old and was forced to withdraw from the 1983 Masters before the second round.
Which gets us to why Tiger lost his shot to catch Jack's record of 18 career major championships: He is just not giving himself enough opportunities. Nicklaus' frequency of wins slowed down in his late 30s and early 40s. But he was out there every time and had more opportunities. Woods is not and there is no indication it will ever get better.