In some places they are. For instance, net flix appliances use FreeBSD. One of the deciding factors here is licensing: Linux is gpl, meaning net flix would have to contribute back its changes, whereas by using a BSD-licensed alternative, it can keep those changes in-house for a performance advantage. You can dispute the merits or ethics of this, but that's the choice a good few people make. I believe yahoo used it for similar reasons. Some consoles (Sony Play Station 3, Nintendo Switch, possibly others?) use it internally, again so they don't have to open-source console code. Others use it for appliance-type devices, again for similar reasons.