My apologies for the covert edit making you rewrite your reply.
Why is sci-fi useful when we could just look at technology history? It's the range of imagination involved- exploring big possibilities and unintended consequences that are unlike anything we've experienced before. A lot of it is also noticing how historical patterns could play out in a new context, and sharing those ideas.
I am reluctant to list out prescience examples, because on one hand they seem so numerous I couldn't do them justice with just a few, and on the other hand people will disagree with the importance of them.
Overall- I feel like it is a simple fact that lots of tech people and inventors love sci-fi, grow up reading it, and then it influences what they think about and choose to work on. I suspect we wouldn't have had rockets or space travel when we did, if we didn't have so many victorian era books imagining space travel. The numerous billionaire pet project space companies we have now seem a lot like people trying to live out fantasies from reading Heinlein. Even little things like the devices we have- my Kindle looks and acts exactly like the e-book readers in The Next Generation, for example.
When my son sees old Star Trek episodes very little is remarkable to him except the big things like warp drive and transporters. The "advanced tech" they use day to day is all stuff that is a normal part of his life- 3D printers, tablets, ebook readers, video conferencing, mobile communicators/phones, etc. Same with the "Back to the Future" movies- they travel to a future filled with various electronic gadgets that are very similar to those we now have, but didn't exist at the time... and my son doesn't see how remarkable that seemed to me as a kid, when those didn't exist.
As a researcher in biotech, some of my current research is definitely inspired by sci-fi, especially biotech and nanotech from Neal Stephenson books.
Edit: found this interesting list on wikipedia https://en.wikipedia.org/wiki/List_of_existing_technologies_...