At the moment Web developers are forced to create hacks in order to accommodate multiple Web browsers. Writing hacks takes time and time costs money. That's why Web developers advocate standards so vigorously. Not because we're ideological but simply because it's so inefficient to have to code for multiple browsers.
You say that Microsoft has been criticized, in the past, for breaking backwards compatibility but do you really think that Microsoft would be criticized trying to adopt the W3C standards?