This is how I think about it. It's insurance money. If you're a manager of a big company like IBM, Microsoft or Google, you have to align your current product portfolio and future portfolio in such a way that shows your investor that your company will keep growing, even if your current products are stagnant. You can surely say Quantum computing won't do much in next 5 years. But what about 10 years? 20 years? 30 year…
But the big research plays (bell labs, xerox parc) seem to get less and less funding if they exist at all. A lot of the inventions of those places were monitized outside those companies. IBM had a chip fab in the research building… long spun of was that business.
At the turn of the century IBM was researching quantum computing, but as I was leaving selling services was IBMs big push.