I wouldn't be surprised to see steam cards show up in retail establishments
The entire point of Steam is to avoid retail.
A lot of people don't have credit cards, usually due to age. Those retail cards are useful for the 17 and under market. Regardless, if they try to force Steam Wallet on me then I'll stop using Steam. Buying things on Xbox Live was a miserable experience due to the whole points bullshit.
Playing: Dark Souls 2: Scholars of the First Sin Watching: Mr. Robot