Browser wars: what's the point?

Obviously the consumers benefit, but on the other end, we have companies spending oodles of time and money on a product that they’re going to be giving away. I just sat through a 30-second plug for IE9 – that’s a decent amount just in production costs, to say nothing of getting it aired. Granted, Microsoft has money to burn, but still.
Firefox I can understand – it’s reactionary. And IE and Safari are part of the computer’s environment, effectively serving as advertising. But Opera? Chrome? Netscape?