I believe it's either (a) a lack of understanding of _why_ one should use SSL or (b) a mistaken sense of principle of standing up to the perceived bulliness of Google, which, come to think of it, it's basically an application of (a)
But Google has been bullying around with their behaviour. I don't think that's even debatable.
Netscape Navigator did this (almost) 20 years ago.
EDIT: Link. http://www.kentlaw.edu/faculty/rwarner/classes/legalaspects/...
Oh, wait.
http://blog.elliottkember.com/chromes-insane-password-securi...
And if you disagree with them, you're "a novice".
If you don't set a master password, then your passwords are (presumably) encrypted with your google account. So anyone using Chrome that's logged into your google account will be able to view the passwords via settings. So just don't let malicious users use your Chrome?
Edit: And there's also a guest mode for Chrome, but they can just exit out of the window and run a regular instance of Chrome to use it under your profile.