They may not make money from desktop users, but all their historical actions indicate that the desktop is very important to them.
> Where's Steam going to go? How can they be certain that whatever distro they switch to won't eventually abandon 32 bit? (I mean, I guarantee they will.). Will they then go back to Ubuntu? Or a third distro, then a fourth.... Why don't they just fix their problem now and get it over with?
Well, look at it from this perspective: from a technical perspective this is hard to solve, and the project that they use in order to make this possible (Wine) seems to be lost on fixing this. If Valve doesn't make much money off selling Linux games, they're not going to invest resources to fix this problem Ubuntu has just created. The big loser here is Ubuntu users. And the "fix" involves fixing 32-bit Windows binaries, which from a practical standpoint none of the companies that were only releasing Windows binaries in the first place are ever going to fix this. This isn't about games, this is about software compatibility, and Ubuntu just announced they don't care that much about it.
Valve doesn't care as long as SOME distro supports what they're doing, and there's definitely going to be some distro that says, yes, supporting gaming is worth it to us. Also, if you care about Linux on the desktop, companies like Valve are who you WANT on your side. The last thing you want to do is alienate a company like that, and have other companies say: "well, look what happened when Valve tried to support linux"
If you're building a platform, which is what Ubuntu is, the last thing you want to say to potential users is: "you can't do what you want here". Games may not make Ubuntu money and they may not be on the radar of a lot of users, but being "the platform that's bad for gaming" and "the platform that can't run Wine apps" is a bad look.
Also consider who has the leverage? Valve is offering a massive catalog of games that can't be easily obtained any other way. Ubuntu is is competing with other distros, Windows, and older versions of their own software. And they have virtually zero lock in -- if I want to use a different linux distro it's pretty easy. If I want to get the games that Steam offers in an alternative fashion, on the other hand, in most cases I'm SOL.
So Ubuntu has essentially zero leverage here, and worse they're shooting themselves in the foot for no reason, since nobody forced this on them. As the article states, Debian still supports this, so in a sense they're going out of their way to make life more difficult for their users.