Software engineering is predominantly problem solving and the important traits are analytical and logical thinking. 4 years of education doesn't govern these. Some people have natural pre-disposition to these skills and filtering out people based on majors will reduce your pool significantly.
I've seen a lot many good engineers coming from the Philosophy, Physics and Mathematics majors. And I think this could be true for other majors too.
In short, smart people will easily catch up with what is taught in 4 years and hence given an average employment period of ~30yrs it's ridiculous to decide employment based on a major.