When you have 100+ applicants for a job, you have to apply a filter. Requiring a degree is an easy one to apply that your boss will support. Whether you get the best candidate or limit your hiring pool is immaterial.
A guy I met years ago at a very large company had another filter - he used to split the pile of resumes in two, and throw half in the bin. He then said "I want the guy I hire to be lucky".