In addition to the advantages of Matlab mentioned by others, a lot of uni/college freshman level (and even upper level) STEM curricula include one or more courses involving Matlab. They've gotten themselves included in a few textbooks as well.
>I just dislike contributing to the market share of software I could never afford to run on my personal computer.
I agree and that's one reason I tend toward OSS in courses I teach now, unless there is no practical alternative.