Maybe not all, but some did. Having matrix operations on my HP-15C certainly helped in my circuits exams for solving the simultaneous equations that resulted. And as far as the professors were concerned, solving the simultaneous equations was not the purpose of the exams, so they didn't care /how/ one solved them. The exam was on being able to setup the right simultaneous equations to arrive at the ultimate solution, not on the actual algebra of solving simultaneous equations.