It's hard to design systems that punishes players and still retain engagement. I believe this is why tadpoles ended up being all kiss and no curse, or now just change your appearance. Just the assumption alone can be a huge deterrent, and the initial narrative is essentially echoing that in that it's rooted in "finding a cure" for the tadpole before you turn into a squid. That + suspicion of the emperor was more than enough for me to pass on using any of them.
From Larian's PoV, you spent all of those resources developing the illithid powers and hamfisting it into the story, unsurprising they made it consequence free and I think the only reason there isn't more obvious encouragement is it would undermine the entire foundation of the story
