Does there need to be a common theme for STEM triple major?

I checked the Graduation Majors report and over the last 10 years there seem to be around 10 students each year graduating with a triple major at his school; one year had 18. That’s not to say he should do the same, but I guess that is why the idea is in his head. He is my only, and I had never considered more than one college major for myself, so I do really appreciate everyone’s responses and insight. I am hoping with the school’s guidance he will figure out a successful path.