If Chrome was concerned about your sense of security it would inform you that all your saved passwords are clearly readable in plaintext at chrome://settings/passwords. It would do this each time it saved a password. It does not do this because you would be less likely to trust Chrome with your passwords if it did that.

So Chrome wants you to feel secure and give you convenience. Either it makes some attempt to prevent casual password access or it informs you that your passwords are casually available. It can't have it both ways.

I agree that the user would be better off having the vulnerability rubbed in their face but Chrome does not do that.

Edit: You also need to take into account intent and the emotion of the user accessing the passwords. The system currently implemented in Chrome makes it easy to peek at someone's passwords without malicious intent. If you simply had to overcome some hurdles it would make most people stop and think about what they are doing because it is a breach of trust. We're not talking about stopping determined attackers.

Edit 2: Also, I presume that specific environment because it is the environment I work and live in every day. We bring our personal laptops to work, we debug code on each others' machines, and we occasionally step out of the room. Sometimes at home I take a friend's laptop to look something up, sometimes I lend mine. I think these are common scenarios for computer users (though admittedly I have no evidence for this).