Seven to 10 years to completed a doctoral in education!

Recently, I worked on the studies of non-traditional students who returned to graduate school. Precisely, the teaching professionals at one of the stat university in the Midwestern. Astonishinlgy, I discovered that over 50% of them completed the doctoral degree between 7 to 10 years! here are some of the statistics from the office of graduate Studies:

Areas of study and percentages -
Curriculum and teaching: 38.5% in 5 years; 59.6% in 7 years; 86.5% in 10 years.
Educational leadership & policy studies: 50% in 5 years; 83.3 in 7 years; 100% in 10 years.
Special education: 33.3%; 69.7 in 7 years; 90.9% in 10 years.
School psychology: 0% in 5 years; 20.0% in 7 years; 40% in 10 years.