Stuff like this is highly context dependent. It is a good thing that apt asks about each step. I voluntarily add more of this by opting for things like listbugs. If I then decide to override such protections with a -y for whatever reason that's a choice on my part to prioritize convenience.

Either way it's got nothing to do with security - I was never going to catch a vulnerability in the central debian repos by reading a list of dependent packages.

It's kind of the opposite. The more typical Unix nehavior is to just assume you knew what you were doing and meant it, and not ask for confirmation in the first place. -y is just the reversion of an abberation.