@Ian2: That's also pretty close to the truth because a lot of designers don't realize that you don't design for the web the same way you design for a magazine or brochure. I see it all the time; a design company sends these beautiful PDFs of layouts and they're things that are particularly difficult to achieve in HTML. They do things like using custom fonts they don't have licenses for, and making fonts different sizes on every single page so all these little boxes line up (using fonts as a design tool is one of my personal pet peeves about non-web-designers).
Not only that, but once we get it 95% of the way there, they tell us they want us to be compatible with browser versions 6 years old. Web standards are already unbearable as it is; go back 6 years and it's like the dark ages. That's why I'm not so surprised that bad browser checks are so prevalent in the "wild"; it's the only way to shut some people up who don't know better. All they see is that 3 people hit their website in IE7 last year, and darn it they need to see content correctly too!