Maybe Valve has not directly received revenue from these gambling sites, but they have absolutely profited from them indirectly. They also evade directly answering if they've ever coordinated with these sites in any way, which is the accusation that's been made.
They may have maintained plausible deniability, but they were absolutely complicit in enabling this illegal gambling operation to thrive. They're not stupid, they closely monitor their community, and they knew exactly what was going on. They should've fixed this a long time ago, and they're only now addressing it because federal regulators are stepping in to put a stop to it.