The AIs are supposed to be very expensive, but it's left to the reader to figure out why—maybe it wouldn't work out that way in real life, but if the reader can't explore every part of the economic and technological space of the world (they can't), they become immersed within it, and allow the subconscious to come up with reasons for why such technologies exist in the story.

What's interesting in sci-fi at the time is that, because software wasn't fully solidified as a concept (nowhere near, in the case of Neuromancer) everything acts like a tool. What you buy stays just as it is, until it becomes obsolete. There's something quite appealing in that completeness. As you say, software is jarring in a way firmware isn't, and it lets developers be lazy.

As for toilets:

> Sometimes he resented having to leave the deck to use the chemical toilet they’d set up in a corner of the loft. - Neuromancer