There's a whole subset of folks looking at 'tech' as 'startup', and the goal of those companies is often to get acquired, so, the company won't necessarily be around in 8 years, let alone 20.
I've resigned myself to the notion that I'll never get a '20 year anniversary' at a company at this stage of my life. I don't mind, but it was one of those things when you're younger that does seem achievable. Most of the companies I've worked at in the past 25+ years aren't even in business any longer, except for 1, which was already 15+ years old when I started, and that was 15 years ago - had I stayed, that might have been the one chance to hit a '20 year' mark someplace (and I have one colleague who started with me and stayed there, so he might make it).
I won't either. But I was at one company about 13 years, another about 8, and just over 10 at my current one.