You’re not missing out if it’s coming back again - for instance, fear of missing out summer makes no sense.
Missing out Halley’s comet, on the other hand…
I hope that clears up your confusion.
These are false equivalencies. Why not make them available all the time? Have you ever asked why they don’t? Because them going away for an unknown time drives purchases. Now why does it drive purchases? Because people are afraid of missing it. You can get it eventually sure, your just punished for not getting it then and have to wait. It’s textbook FOMO marketing, saying it’s not is just silly.