Many students who have intentions to do 3-2, end up not wanting to leave their friends at their LAC the year before graduation there. They end up w no engineering degree,
Those who do transfer end up paying for AT LEAST an extra year (5 years total), if not 2 extra years (6 years total) because they have a hard time scheduling the requisite courses within that period,
Then there’s the pesky issue that you need to apply and be admitted into Columbia or other school. Admission is not guaranteed.
Also, financial aid after transfer is at the discretion of the “2” school. Columbia does not promise as much financial aid for 3+2 transfer students as it does for frosh and other transfer students.
For higher income (not eligible for FA) students receiving merit scholarships at an LAC, 2-3 years of fullpay at Columbia is a very unattractive financial proposition.
The reason many students who start as an engineering major but switch is because of the difficulty of the curriculum. This change takes place at all schools not just those who think they want to pursue the combined engineering program. And this change takes place mostly in the freshman and sophomore years. If a student can get through Calculus I - IV, Differential Equations, Linear Algebra, Physics I and II, Chem I, and Comp Sci, there isn’t much else engineering can throw at that student to deter them. By the time a student is done with all these foundational courses they will know whether engineering is for them or not.