I'm F2P, so the only way that we can get gems is via the free route of the brawl pass. This season, it gives 90 gems, and it can be expected to stay roughly the same. However, the brawl pass costs 169 gems. Hence, we can only buy the brawl pass about half of the time, then we would only have 11 gems every 2 seasons to spend elsewhere.
I srsly hope they'll bring gems back into boxes. This is my thoughts:
Chances of finding gems in a brawl box: 10% IF MAXED OUT. This should be low enough for Supercell not to lose money.
If you DO get gems:
30% chance of getting 1 gem.
40% of getting 2 gems.
15% of getting 3 gems.
8% of getting 4 gems.
6% of getting 5 gems.
1% of getting a "jackpot" 8 gems!
This means that you'll get an average (arithmetic mean) of 2.25 gems if you get any, and hence an average of 0.225 gems per box. This is very low and won't harm Brawl Stars's income.
On the free route, we have 161 worth of boxes. This will give about 36 gems more. On the Pass route, there are 90 boxes, about 20 gems more. Additionally, every 500 tokens thereafter you'll get an average of 0.675 gems. To convert that to whole numbers, that's 135 gems every hundred thousand tokens.
And remember, these odds are if you are maxed out. Supercell could reduce the chances if you aren't maxed out. The point of doing this is so that gems are easier to obtain. To be fair, after calculation, it does seem that you'd be getting an average of 90 gems per season. But now Star Points, for example, lose value. Also it's less "exciting" and it's so much more predictable. On the plus side, you can plan out exactly how you want to spend it. On the not-so-good side, you're LIMITED to 90 gems per season, no matter how dedicated you are. It doesn't feel good to know that you'll get the same amount of gems playing every single day and getting every single quest compared to someone getting 22850 tokens in one season only. Especially since I can't get any after completing the road. Plus, when I'm maxed out, the only currency I care about is gems. Personally I'm not maxed out but there was a time where I could only open coins, gems, token doublers, star powers, tickets and brawlers from boxes. It really stinks to just keep opening coins.
So please Supercell just let us get gems from boxes or some other way after completing the Brawl Pass. Or make everything free. That works too.
This turned from a "why gems should be added back to boxes", like a 3-liner, to a long post about how to do so and detailed "why". I understand why Supercell might disagree with me, but feel free to argue with or against me.