Earlier quoted context omitted.
It seems like a case of motivated reasoning. Doctors needed to operate on babies; anesthetizing them would be hard. So they decided that babies can't feel pain and never investigated methods of anesthesia on babies.
More like anesthetizing them would be risky and they're not gonna remember it so it's not worth the increased risk to their life since infants are already fairly fragile and saving their life is the primary goal. It's not just "it's hard and we're lazy so lets make up an excuse" like you seem to be implying. Edit: Since apparently it wasn't clear, we're talking about the timeline when this issue was hashed out, so th…
It's one thing to say, we're not going to use anesthesia because it's too much risk, it's another to say that they don't feel pain at all so let's not worry about it.