First off every branch has their own criteria.
ROTC is generalization, you need to specify even further regarding which branch besides your NROTC comment. Army, Navy and AF all have different systems.
N/AFROTC offer @80-85% of all scholarships to STEM majors. It is driven from HQ that this is what they are placing an emphasis on for their future missions.
They don't need a French Art History major, nor do they need a ton of marketing majors. They need engineers and STEM majors because of technology.
It is all about the budget and dollars and cents. I can take a STEM major and put them in Public Affairs, but I can't take a French major and put them in maintenance. Best bang for your buck. In the AF world yrs ago it was explained as this:
You can take a pilot and make them a Maintenance officer, you can't take a maintainer and make them a pilot.
I can't speak for the Navy, but I can tell you AF really places an emphasis on STEM.
Type 1; 5% of all scholarships, only 5% of that 5% goes to non-tech majors.
Type 2: 20% of all scholarships, only 5% goes to non-tech---if I recall correctly
Type 7: 75% of all scholarships, the bulk of non-tech come from here.
WARNING to posters and lurkers Class of 17, do not think of gaming the system. In other words, apply tech to get the scholarship and change majors once in college. AFROTCHQ will require approval. No approval and you are stuck in that major. Chances of approval in this current DOD budget is slim to none.
Army from what I have gathered through this site is still easier to obtain a non-tech major, but they are changing it now towards tech majors.
The other reason why I asked what branch is because AF does not care which college as long as it is on their list, they care about the major. Navy and Army does when it comes to that college list and major.