The generic argument is empty. Firefox is good for Mozilla's business. Same for Opera.
The business cases for IE and Chrome are significantly different. Distributing IE with Windows benefits users for the same reasons that Ubuntu Linix distros ship with Firefox - they providing a rational and reasonable path from the act of stuffing an install disk into a drive to the point where the user is surfing the internet and possibly completing the installation. IE allows windows to be used right out of the box.
It's hard to make that sort of case for Chrome - but easy for Safari. Chrome was primaily developed to improve Google's data mining and reduce search server loads by collecting keystokes from the address bar.