OK, let me try. MIT students have done well in their academics. If your passion is a STEM EC, then so be it. But most students have other interests as well as STEM interests. It does differ quite a bit from high school to college.
There are so many more opportunities to do non-STEM activities at MIT and in the Boston/Cambridge as well as the whole New England area. Not as many opportunities in high school.
In the applicants I have interviewed I have seen many who are into Boy Scouts (not so many into Girl Scouts), sports (both at the varsity level and just for fun level), music, photography and few who were into cooking. I even had one interview where the student brought her water color art work to show me. Of course, I’ve had several who were into some kind of robotic competition. But more often than not, they had no formal STEM ECs.
Once you get into college, the expansion of the opportunities brings out the passion in many different areas. Music, both making music and listening, was a big one. Friends would make occasional trips to the Boston Museum of Fine Arts or some of the other smaller art galleries. Several of my fraternity brothers (including me) were into varsity sports. I also learned how to sail. I learned to cook foods from various regions of the US from my friends and somethng about German cooking (which wasn’t my favorite) from someone who grew up in Germany. Others got into politics, still others into literature and writting. I was a civil engineering major but also studied architechture. I was specifically interested in the evolution of home design in New England from Colonial times thru the early 1900’s. Just look at all the clubs that MIT has. Look at the offerings for Independant Activities Period (IAP, roughly the month of January); I recall glass blowing and ballroom dancing as a couple of the many offerings.
MIT is an amazing place and what makes it even more interesting is the varied interests of the students.