Kids media is full of sentient machines, from Thomas The Tank Engine to Brum, these things trundle around as of their free will, sometimes even holding their human counterparts “hostage” as in the case of Thomas where the human seem to be mere observers of the activities. 

What do you suspect the purpose of this is in placing this in kids media? 

Are we anticipating a rise of the machines type scenario, where Arnie comes strutting out of the smoke, double barrels peering at you like twin eyes of doom?

Unlikely. 

More likely they just make great conveyers of stories, we often add human qualities to things, it’s called anthromorphism, it’s got a name for getting out loud, it must happen right? 

The other likey solution is that they can sell toys of these things, and trains and cars are far easier to manufacture than likenesses of people.