Companies that have so much cash they can employ 100K+ developers on top of goodness knows how many designers, PMs, POs etc. of course they hire and fire. They can afford to offer above-average conditions when the markets need it and everyone goes flocking there only to be surprised when their job is taken away at the next point the shareholders are bothered about ROI.
If you want to ride the unicorns and take the risk, that's fine, but there are plenty of people around the world who have far fewer choices with their work and are paid far less so I don't feel too bad that someone's Christmas might be not as expected.
If you want job security, get a job somewhere that isn't trying to earn their next billion, where you can make a difference, where you are appreciated and where work/life balance means something. I expect you would feel much better :-)