Quick caveat- this is my opinion only, based upon our experiences- if others have more knowledge, please share- we had specific goals in our DDs college search (we did not explore extremely large universities, for example).
The quick/simplistic answer, as far as I understand it, is that colleges don’t have graduate students or programs. So by definition, one of, if not the main goal, is the education of undergraduate students. Many, but not all, have as a secondary goal more of a broad view of education and therefore may have core classes or distribution requirements, theoretically ensuring that their graduates are more well-roundedly educated while still requiring a major area of concentration.
This can get really murky, however, in that many (?most) universities have colleges within them, some of which have separate admissions, some of which do not, some allow students to take classes enrolled in one college to take classes in all the colleges and to transfer if their major/plans change, some are more restrictive. Even within specific disciplines, we found there to be a lot of variability in this structure.
Because our DD still has several areas of interest and hasn’t decided on a definitive direction yet, we avoided those schools which required admission to very specific programs or schools, as they didn’t have the flexibility she wanted.
