And every CAS softwares (Mathematica, Maple, Maxima, SymPy, etc) have sometimes limitations and bugs. I'm a physicist teatcher in university (UFES, Brazil), so when my students how to know to use a CAS I asked them to solve very hard problems (impossible by hand) CAS are useful not only to calculate what we can by hand, but mainly to open the doors to solve more complex and realistic problems (in physics, enginneering, etc).