Because that's what Richard Branson does. It's all theater, and Kabuki at that...
Virgin Atlantic has over 20% of the US-UK traffic. BA and AA combined have 47%. He's afraid he'll lose share, which he likely won't. Virgin has an excellent product (and that includes Virgin America and V-Australia), and people fly the Virgin branded airlines because of that.
Hopeful, I think you know by now the revenue battle is fought and won with the customers in the front cabins. The number of aisles doesn't matter up there.
I'm not talking about Jetblue -- Virgin America's product is far superior -- just to start, they've got 110v power outlets at every seat; AA has 12v power at 20% of the seats in coach. They've got a real on-demand video system *and* live TV.
Their first class is better than AA's business class product, and is half the price (AA offers its "instant upgrade" fare but that's limited availability). They've also got "main cabin select" which is premium economy -- 38" pitch and again, half the price of AA's coach fare with 32" pitch.
I've flown Virgin, and it's worth not getting the AA miles. I'd say it's worth paying half the price of AA, but even if it were the same price, it would be worth flying on them.