The setting itself tells us that something must be happening. It is a biocentric milieu; if there were no downside to using robots, it wouldn't be. The existing rules happen not to explain what it is that's the fly in the oinment. Is that because robots work perfectly and last for decades? Or is it because PCs usually don't need to worry about their robots lasting for decades and any risk of failure is subsumed in such rules as a natural roll of 2 is an automatic failure?
The setting itself says, "A tragic attack against the Sylean Federation, which occurred in -112 in Core sector, helped shape the Third Imperium's current attitudes about robots. A terrorist group rigged one of the Dover-Gabe courier robots to self-destruct, and managed to sneak it aboard a 90,000-ton Sylean battleship. The Empire's Banner was on a goodwill mission in orbit around the world Fornol (Core 1715) when the robot's hydrogen/oxygen fuel-cell exploded. Fornol's premier, two ambassadors, and the Sylean vice-minister were killed, along with a host of ship's officers and crewmen.
The repercussions from this event were so far reaching that the Sylean Federation was nearly thrown into a civil war."
"This disaster prompted twelve worlds of the Sylean Federation to meet on the neutral world of Shudusham to draft an agreement dealing with the issue of weaponry carried by robots."
And later, "...Interestingly enough, the Shudusham Concords encouraged low intelligence in robots, to prevent them from being versatile enough to be used as attack robots unless specifically programmed to do so."
In other words, canon says it's a biocentric milieu not because of something currently happening but because of long-term consequences of past abuse. The "fly in the ointment" is a conservative culture in which the long-term effects of a thousands-year-old interstellar agreement evolving from a shocking incident, an agreement limiting the performance of robots, continues to guide laws and customs in the "current" age. Canon says that the Aslan and Vargr similarly have cultural restrictions limiting the use of bots (for different reasons); that the Zhos are heavy users of bots but that the nobles prefer directly-controlled lower-intel bots to the more independent high-intel bots (and at TL14 don't generally have access to the same levels of intelligence the Imperium might have, were it not hindered by cultural practices); and that, "Hiver robots are sophisticated and robust, able to 'handle themselves' In a variety of environments."
Given that the Hiver's TL15 bots, "...diagnose and treat illnesses, advise on legal matters, negotiate treaty terms with member races, and perform many other tasks which would require years of training for a living creature," and that, "Some Hiver armies have consisted entirely of warbots, with no living members," it's clear that Hiver society is not so biocentric as Imperial society. In fact, the claim of all-bot TL15 Hiver armies bodes well for the potential of TL15 bot pilots
Yes, but would you use the non-existence of rules for breaking and losing hammers to prove that the organization of your choice never buy new hammers, because they bought all they needed many years ago and hammers never break or are oost; the rules say so?
I would - as I think I made very clear - argue the nonexistence of rules to imply that the incidence is low enough not to need rules to cover the event. Players hypothetically are at risk for strokes and heart attacks, but the incidence is low enough that it's silly to roll for them during the course of an adventure. Companies lose employees to such events regularly, but it doesn't mean they stop putting humans at the controls because humans tend to die at importune moments.
Whether the incidence of loss due to a robot pilot encountering something it can't handle - that a human pilot could - is low enough, that's a gamemaster decision and therefore an IMTU thing. Consider the case of the aforementioned xboat: if they lose less than 1 in 50 xboats over 20 years of operation, then they are ahead by replacing the human pilot with a bot; if they lose more than 1 in 50 over 20 years, then they lose money by replacing the human pilot with a bot. Either event's a very low probability, but they would affect basic business decisions. They would be beneath the rules, too infrequent to bother with on a trip-to-trip basis, but they would influence the "texture" of the milieu because businesses would make long-term decisions based on those probabilities. In this instance, since we are presented with an Imperial culture that tends to reflexively eschew use of robots in critical positions, the milieu itself does not inform us, and it becomes our call as gamemaster as to whether bot pilots are cost-effective or not - unless there's some element of canon that speaks more clearly to the issue, which is kind of what I'm asking.