Maybe it doesn't with the private industry but it should. Fractional reserve is fraud made legal, plenty of bankers have been lynched after runs on supposedly full reserve banks in times when it was a crime and tolerating any possibility of it with Bitcoin allows the same thing to happen, 10 times more on the books than in the vaults.
100% agreement here, just the normative evil of the world. I urge you to check out the FDIC website regarding historical reserves since the 70s. They publish yearly values. If you look at their ratios, you will soon realize that even the FDIC hasn't remained solvent (they are public). They are below a ratio of 1:1 many years now. It's quite sad, but the system is backed by the Fed which is backed by the USG. Centralization allows this to occur unchecked.
If some exchanges and services can operate with full transparency and store everything in user controlled wallets then why can't others? What do they have to hide? Anyone not asking that is irresponsible with their coins and deserves to loose them.
They don't want you to know because it relinquishes their control on you as a customer. If you don't know, you are forced to believe in them and form a bond of trust. This makes the equation one-sided and it doesn't benefit the customer (us). This is what they want.
We can ask all we want, take our business elsewhere, etc., but if mainstream gets it, you can bet it will go this way. The sheeple do not care about transparency. It is not important to them; I'd dare to say most like not having to make any decisions of their own. It boggles my mind sometimes.