Right, those would have the biggest incentive. But I'm sure good fundraisers will be bale to even get some large companies that aren't engaging in the standards at any level to throw some money to support a standard web browser, if they can convince everyone that without this there won't be a good way for people to access their web sites.
I suspect that the leading reason browsers require so much investment and development effort is the ongoing effort to engineer them into heavily surveilled application delivery platforms.