Because spam is incredibly selfish.

You're trying to take the time and attention of as many people as possible, without regard for whether or not they'll benefit.

One safeguard people have is knowing that it costs something to send in some way to contact them. I'm this case, the sender's time and attention. LLM spam aims to foil that safeguard,. intentionally.

If an LLM will take care of other LLM emailing me, their last point comes true, no? I never have to deal with spam.