I mean, surely the answer has to be: "because it's a pain point and there's a market for it", no? In the sense that, I think your skepticism is (rightly) warranted, but only because of the outcome that you've seen so far has produced unsatisfying results. In a universe where this approach does yield consistently correct and succinct answers, having an AI read a large body of technical documentation and be able to serve you the exact answer that you need from it does seem like a solution with lots of takers!