Personally I don’t really mind that these aren’t visible like the rest of the cases, for the sole reason that there’s no way for you to acquire them with real-world-money. They are only available through daily rewards, so there isn’t really much “need” to know what the drop-rates are in them.
Legally, SD don’t have to give the drop-rates of cases at all (just look at Overwatch - if it wasn’t for China’s publishing law on gambling, we’d still have no idea what the drop-rate for bogus shiny things were), but the fact that they do is actually a really nice bonus. 
Personally I’m happy with MK cases just being “X rarity or above”, with a “higher chance” of better rarities than regular cases. Knowing the odds is actually a bit of a catch-22 as well, because if FOR EXAMPLE the drop rates were as follows:
- 70% Iron
- 15% Bronze
- 7.5% Silver
- 5% Gold
- 2.5% Cobalt
Now if you got 10 of these and got 10 irons, how would you feel? Pretty screwed out of luck, right? I’m sure everyone who’s ever bought elite cases has had that feeling before - I know I have! This is exactly why games like Overwatch DON’T publicly release drop-rates for RNG items, because people will look at the raw numbers and expect exactly what they say.
Would I like to know the drop-rates for MK cases? Sure. I just really don’t think it’s majorly required, considering you can’t buy them. They are a nice extra source of boosting players (especially new players) card collection, while making them feel just that little bit better about seeing iron, bronze and even silver+ much more often. This is why I personally don’t have a problem with it 