Yes, there is some value in using C for teaching these concepts. But the problem I see is that, once taught, many people will then continue to use C and their h

Yes, there is some value in using C for teaching these concepts. But the problem I see is that, once taught, many people will then continue to use C and their hand written byte swapping functions, instead of moving on to languages with better abstraction facilities and/or availing themselves of the (as you point out) many available library implementations of this functionality.