In this sense Valve does not engage in "fraudulent advertising" because it is well understood that they sell licenses, not complete copyrights for software products. Or in other words: You buy a right to use the software in a limited way, you do not buy the complete copyright and full intellectual property. And giving your license to someone is really noting more than handing them proof that you are the rightful user of said license. The license itself is not transferred.
You are operating under the false assumption that buying software means either buying a license to the software or buying the right to make copies and derivatives of that software. There is actually a third choice: buying copies of the software. When you buy a disc for a game console you are free to play, lend, and resell it without permission (see the "first sale doctrine"). You are buying a copy, and the right to use that copy is implied; it requires no explicit license.
So... is buying a game on Steam like paying for a license, or is it more like buying a copy? Valve wants us to think it's a license, but it sure does feel a lot like purchasing a copy at the point of sale.