Because the law says they have to. In some settings, privacy and wiretapping laws will apply to using Glass. In some other settings, they won't. Different US states have different laws governing the use of audio and video recording hardware in private versus public settings.

Glass is going to force new discussion about one-party versus two-party consent to recordings. It's a conversation that needs to happen.

Because they're required to by law, as telephone conversations are not considered public.

Walking down the street, on the other hand--

I'm not really arguing about the details of how current laws are, I'm arguing about the morality of technology and how the laws should be.

If I'm talking to you over the phone, I'm allowed (both morally and legally) to remember your conversation. I'm allowed (both morally and legally) to write it down, to remember it better. And I'm allowed (both morally and legally) to remember it perfectly forever, if I'm able to.

Should we legally forbid to actually fulfill that if I need some assistance to remember it exactly as happened? My fuzzy memories and notes are allowed, why should better, exact memories/notes be forbidden?

I'm allowed and may be even required to remember past events in courts - should we forbid remembering things as they actually happened and require them to be stuck in the noisy, lossy and distorting channel that is homo sapiens memories?