Pretty much what happened with Speech Recognition for 30 years. That last 10% had to be handled manually. Even if you get 90% right, it still means ever second sentence has issues. And as things scale up the costs of all that manual behind the scenes hacking scale up too. We underestimated how many issues involved Ambiguity - where N people see the same thing and have N different interpretations. So you see a whole bunch of Speech Rec companies rising and falling over time.

Now things are pretty mature, but it took decades to get there but there is still a whole bunch of hacks upon hacks behind the scenes. Same story will repeat with each new problem domain.