Microsoft Windows was vaporware for years. They famously did a "demo" that was just a manipulation of graphics.
But Bill Gates correctly grasped that the future of the business rested on it and set about building the brand.
Apple was way ahead of Microsoft with windowing technology. Gates even offered to help Apple port it to the x86 architecture. He was content with being the dominant application developer, not the OS.
Jobs blew him off so he seized the opportunity.
Around the same time IBM was working on OS/2, which was a much better technology than Windows. Microsoft worked with IBM on OS/2, but then gaslighted them by "debuting" Windows 1.0
Edit: And don't forget how me VC pitches are about "what we're going to build" vs. "what we've already built."
Vaporware is not an optimal strategy, but in many cases it works.
If they actually had the software already...
No one sets out to lie. Gates would've preferred to demo the real thing. But in the context of that market, "we'll release that in two years" is worse than vaporware if you want to actually own that market.