Michigan Tech has a somewhat more limited selection of majors than many more general schools. Also, more than half of the graduates are in engineering majors.
http://www.mtu.edu/admissions/programs/majors/alpha.html
http://nces.ed.gov/collegenavigator/?q=michigan+tech&s=all&id=171128#programs
So students who change major may be more likely to decide that they would rather study their new major at some other school where the major has more offerings, faculty, and students.