Well, essentially you have the language used in the class match the subject being taught.
Python gets language difficulty out of the way of learning a given algorithm. Bonus points for exacerbating the time issue when trying to introduce Big O timing notation. The kids can actually "feel it" in an in your face kind of way.
Systems, it's different, as you say.
Compilers. Different AI courses. And on and on. Each you may have legit reasons for using different languages.
The concern starts to grow when Python is being used across many courses to the exclusion of any other language or technology. That's the issue that's growing across CS departments right now. Couple that with kids who have no interest in learning the other languages on their own and voilá! You have an issue with uninterested kids graduating, but now they're also unprepared.
