Why? The NP almost uniformly like and trust him, and assuming he was persuaded that NP souls should be Guided in the first place, I think he'd be happy to do the job. All the other psychopomps lean into the divine titles and imagery, so I don't think it's a problem if Robot does the same. And we know he approves of robots having a "proper death."
Assuming you have the powers and the stamina for it, it's kind of a hard job to mess up. All you really need is rizz so the souls don't argue too much.
(yes, Robot's been misleading and manipulative, but I think you can put that under "career-relevant skills" when you're applying to be a Guide.)
Well, the NP are wrong in trusting that manipulative son of a bolt. Yeah, the other Guides are also not exactly the trustworthiest bunch, but at least all they do is (as far as we know) part of how to make sure that their job is done as effectively as possible. All was either about getting souls ready to be guided, or recruiting someone new into their ranks. While S13 has lots of interests in the material world right now. He wants to be a prophet to his people, an angel...
He certainly doesn't want to be
thought of as an angel.
And preparing souls and recruiting people to the faith are what exactly prophets and angels do. And often they move in, y'know, mysterious ways. Manipulative ways, even.
I think Robot just wants to do
his job as effectively as possible. The Seraphs exist to
guide and oversee robotkind; that's what they were made for. Diego designed S1 in
his own (heavily idealized) image, and the golems and robots developed a hereditary priestly caste that perpetuated that image. They're like the
Kohanim in Judaism. (And, like the Kohanim, their exact roles and level of authority have varied dramatically over the history of their people.) At first we see them mostly acting as police, but later one is shown attempting a
more benign advisory role.
So, Robot does all the priest things. He interprets the Angel's will to his flock, guides them to a better understanding of her nature and abilities, counsels them in
difficult sitations, and
intercedes with her on their behalf. (If his intercessions are sometimes sneaky and manipulative, well, Prometheus tricked the gods on mankind's behalf as well. And it's hard not to start out creepy when Diego was your first role model for love.)
In the past he did a lot of preaching, but that was because he had to spread the Gospel of Kat. Now that all the robots and New People know that she exists and has a wonderful plan for their lives, and now that Kat's more or less working in public and can just talk to the New People directly, the prophet side of his job is less necessary. I could see Robot coming around to the idea that Guiding is now his most important priestly duty.
OTOH, he might prefer to have the other Seraphs do it. That would keep them out of trouble with the living New People, and they'd probably jump at the chance to get back in the Angel's good graces.
That's not
all they do; they also
squabble over the rights to individual souls, and recruit/train/manipulate potential new Guides like Annie. Presumably they also do stuff to establish "jurisdiction" over souls in the first place, unless that's taken care of by higher deities in their pantheons.
(And their personalities vary. Muut is quiet. Mallt-y-Nos and Moddey Dhoo, less so. Hermes, I would bet, is
extremely chatty.)
So if Robot's still hankering for politics and preaching, he could probably still engage in it as a Guide. He might also be able to continue his work coaching robots through the transition process, since Guides can appear to the living if they choose. Then he could guide all the New People both into and out of their lives. That would be elegant.
That's going a little far. Traditional robot culture confiscates the bodies of troublemakers and heretics, and uses their CPUs for research purposes, but we've never seen Robot punish or suppress anyone for what they thought or said. Even the Seraphs are still alive and free; they're just not respected very much anymore.
Robot's not particularly dogmatic with the transitioning minds, either. In "She Gave Us An Ocean" he didn't try to give the mind a catechism or anything like that; he just emphasized its power of choice over its thoughts, feelings and appearance, and then left it alone. I don't think he'd do anything different with a "misguided" soul, even if Kat would permit it, which she wouldn't.
Now, if he knew that a particular soul's passing would spawn an etheric False Kat...well, I'd probably trap it too, at least temporarily. That prospect is
terrifying. Wonder if the Machine Angel will have to deal with etheric echoes of itself in the future?