appveyor matrix vs tox matrix

I've found many references to use tox and a CI server, like appveyor for Python testing. However, the dependency matrices have confused me. It seems redundant for me and I don't know why to use both, like it acts in several examples. (Appveyor's docs, or an example repo.)

I mean, I will list the same environment-settings under environment -> matrix in appveyor.yml as in envlist in the tox.ini.

Is it really redundant? Then why we use both matrices?