Why revives are so rare?

Ask Niantic support.

You will be always out of what you need! Use your berries and balls and spin those stops like hell!

Try to remove your 'mons from battle before they faint. Powering up also revives them. Stuff you are using a lot runs out fast. I had a lot of revives, but then I went and weakened some annoying tower and here we are, saving revives now.

forget the Gym 1 - 2 week, wala 100revive+++...

You run out of what you use most. Sounds like circular logic. If you are mostly fighting and prestiging gyms, then you will run low on potions and revives. If you are mostly catching pokemon, you will run low on berries and pokeballs.

Plan for a walk or trip some place where there are a lot of pokestops and just focus on catching pokemon. This will be especially beneficial during this double experience event.

If you are in need of coins right away for incubators for this event, then consider spending $10 or $20. Think about how much time it takes to fight gyms. If you regularly cash out with 5 to 10 gyms, then $20 buys you a month of gym rewards.

yeah ok

I believe it has something to do with this festival. Maybe Niantic wants you to catch more Pokémon? I remember this happened when gen2 first came out.