A lot of people fall for the "brain is a computer" metaphysics without thinking about it. I'm not sure why it's so appealing.

It might have something to do with desires for power. Early on, the cyberneticists tried to really push this metaphor (in spite of contrary evidence from neurophysiology) in large part I think because many of them couldn't resist the allure of having a "theory of everything" that could encompass all knowledge through mechanistic computation generalizations.