What do you Mean? I downloaded it from galaxy store and it is introduced in samsung's official website too.
The reason why we chose bitcoin was because we wanted to have control over our own money without needing a third party. Otherwise we would stick to banks and never bother with a volatile money that has very little adoption.
To have that full control you need to know what the tool you use to create your keys, store your secrets, create transactions and sign them, sync your wallet, etc. actually does. That requires the tool/wallet to be 100% open source, transparent and popular enough so that it is reviewed and bug free.
You can't say that for Samsung Blockchain Wallet because it is closed source and relies on the centralized company that creates it and the centralized servers it uses to sync up. So not only you may not be completely secure but also you don't know how much access the company has to YOUR money!