There is nothing unusable about Steam.
Hard to believe, but some people do not want to buy games on steam for several reasons, you cannot resell them, you cannot play them without steam, and steam automatically patches them regardless of if you want it or not.
That loss of control keeps some gamers away, but I think as many gamers that stay away, there are as many that will buy whatever comes out on steam so it evens out. (you basically said it yourself,
I know that With Steam on My PC i will likely purchase any interesting Game that comes along. multiply that by over 1 Million as most of the other steam users will do the same.)
I want a Nintendo Revolution controller TV remote.