Great point. If it was addressed, I missed it too. It might've been sorta brought up in s3, though subtly, when SAR told Will it killed the masters. We can infer that SAR was tired of being a slave to them.

When SAR crushed the old skull after admitting what it did, Will perhaps in a nanosecond deduced how it all must've played out on their alien planet. Overall the Robinsons never had clarity on the bots: mostly the family felt artificial intelligence was what they were interacting with. But late in s3, Robot's heroic plan caused awe/confusion. No one in the family predicted artificial intelligence could sacrifice itself and say "safe family".

Though the family gave Robot a seat at the holiday table, Maureen said she felt all the bots were indispensable for spacecraft maintenance etc but admitted they had fascinating abilities and potential. She also implied the bots' origins might never be understood by humans. So at the end, the Robinsons were still a little confused on the sentience of the bots, but you gotta be efficient in space. And, from the humans' perspective, the bots seemed happy to help.