Web design in America

Since so much has already been written about this, I'll just defer to those people who are much more conversant than I am in these things, and leave my rant to only this:

Why do we have to kow-tow (is that how one spells that?) to the browsers, when we are the ones writing the code?  We have to write code now for three (soon to be four for we Mac users) different browsers that all interpret xhtml and CSS differently.