I would not characterize many CEOs as being "a decorative role, who can be replaced in an instant". Leading may not be hands-on engineering and design (at least, you hope!), but it's certainly FAR from decorative.
Part of the problem is that a CEO plays a very different role in a three person company, a 300 person company, a 3000 person company, and a 30k person company. I have a very difficult time imagining swapping out the CEO of an early round startup without having a major existential crisis.