But. It's commercial. And thus prohibitive to the hobbyists and enthusiasts who are ultimately reaponsible for this kind of network effect.
And while I have a lot of love for octave, without the slew of proprietary packages and functionality available to matlab, it is hard for it to compete in such an ecosystem, despite some nice courses out there that use it (notably Andrew Ng's ML course).
If more people contributed open source packages to octave I'm sure it would become as big a player as python.
(inb4 julia: yes, but julia has other problems)