Why Web Designers code from scratch instead of using or starting with Wordpress?

I've been developing a website for about 10 hours a day for the past four day and it suddenly hit me while I was adding eCommerce features. Why am I not using Wordpress, it has great, if not better, features that I can easily manipulate so as hard as it is I'm cutting out all of my work so far because the Wordpress version looks crisper and I can manage a store better on their admin login side.

So my question is when a company hires someone is it "cheating" to spend a day or two setting up a Wordpress site? And from what I know (as little as it is) web designers start from scratch a lot more often then Wordpress. I'm assuming that has something to do with HTML vs PHP.