No, you are right, it doesn't make it invalid. I guess I just chose to see it as a more fun promotion than say a coal game that is exploited by a few and then ruined for most. I get card drops for games I already own or games that go on sale, I can sell or trade the cards for wallet credit or other cards I actually do want, and then craft badges for games I really like or to improve my level to get more showcases for my profile. I actually chose to spend a chunk of my wallet credit buying up FTL cards to create the full level 5 badge, simply because I love the game so much and wanted something FTLey on my profile. That is why I also paid for multiple cheap FTL profile backgrounds as well.
Everything I see from Valve is "apparent" to me in that they exist to make money and further and take advantage of the basic desires in their customers that make them more money. I can see that all in just a cynical light, or also take note of advantages it brings me. It isn't even costing me money to buy these trinkets, or even beta access, for my account, and what I don't buy I sell to purchase access to other games. I don't expect entirely altruistic motives or promotions from a private company, but I usually expect some benefit to consumers to come from profit based motives. Especially from a private company like Valve that seems to hold its ear closer to the ground when it comes to servicing and pleasing their customers/user base.
I do hope you end up having more fun with this whole thing than you seem to have had so far!
. 