Because it's mildly interesting as gossip. And because Mark 2005 mentioned it first, and I thought I'd put it in context.
The president drinking a beer is probably no more important than Paris Hilton being sprung from jail early. It could hardly less important. But if you spend all day every day mulling over serious and important stuff, you get ulcers and high blood pressure. Dumb stories are, in moderation, a nice diversion.
What it does is give his enemies some other rumors to spread.