Most undergraduate majors require 10-12 courses in the major, and maybe up to three courses from other departments as "co-requisites." But most engineering majors require 15-18 courses in the department itself, plus 10 -15 courses in math, chemistry, physics and computer science as "co-requisites."
In one engineering program I looked at, a "minor" consisted of six engineering courses, plus 14 courses in "co-requisites." I "get" that much, particularly the co-requisites (basically enough for another minor). But the major consisted of 18 engineering courses, three times the "six" for the minor, whereas other majors, require twelve courses (double the six for the minor) as well as co-requisites.
That's 25-33 courses, that is two thirds to four fifths of the whole curriculum, versus about one-third for other majors. Why is that?