If they are concerned about malware then one of the obvious solutions would be safe guarding their play store. There is significant less scam on iphone because apple polices their app store. Meanwhile scam apps that i reported are still up on google play store.

That ledger is controlled/can be edited/changed by Vavle. Valve can delete your inventory and there is nothing you can do. Wouldn't that defeat the purpose of having a public ledger that no one can modify on a whim?

The world is volatile. Syria, Afghanistan, Ukraine, Russia, and in the future who know if China and Taiwan won't become a crappy place to be. The needs to store your wealth and get out of the country quickly is very real. You can't just queue for ATM and holding dollars and gold bars come with significant risk of confiscation or being robbed.