Why would somebody not want a browser that would load and render all pages regardless how well they were coded?
If its possible for a browser to render a page ... even if the code is not perfect, is this not an advantage over one that can't?
You are taking a very strict stance on this issue that does not apply to the real world. People just want it to work. If it words on IE and not Safari they think that IE is better (which is a logical conclusion). The general population does not turn around and blame the site for poor code. They don't think about it that hard. They know two things. It works on the M$ product and not the apple.