Microsoft offers free Win7 Ultimate to many university students. They can keep it after they graduate. 1 copy per student. I don't know if they can sell the PC with it under their agreement - probably not. I suspect that this is much of what you are seeing.
Times have sure changed ..... When I was getting my engineering degree, the university policy was slide rules only .... period. Only as a senior in 1973, did my school first allow the use of those new devices called hand calculators (like the vintage HP35 or HP45 at around $400 each in 1973 dollars .... that's about $2000.00 in today's dollars, so many of us still used slide rules as seniors).
Those devices did not come with a COA ..... just a warning label that too much use can lead to dependancy and possible "lame brain" symptom