Business often don’t care about “bad” code, “bad” graphics, “bad” SEO, and definitely not if it was made with or without CSS or Frontpage.
They care about money.
So the main task would be to translate all that “bad” stuff into how it would make them more money. People like you and I know that (for example) better SEO could (not necessarily DOES) translate into more traffic, which could lead to more business, but a business doesn’t have a clue, and so there’s a very big task of educating them.
If they could choose between a bad site that brings in lots of money, or a good site that doesn’t, their choice is a no-brainer.
tl;dr — most local businesses really are not interested in a site that looks better or has better code. They are only interested in a site that will bring in more business.