And you would be right.
I created the web site, the client loved it and then on my own time, before it was launched, I did it again.
Because I wasn't happy with the "back-end" coding of the web site. Sure it looked great. Sure it worked with all the browsers. But I wasn't happy with the coding. So I spent 4 days studying, got myself a tutor for one of those days. Hit the books, did some research online and then in one day, I completely re-created the site.
The site now loads faster, but other than that you wouldn't be able to tell that anything was done.
So again.... why would I invest all that time, money and energy to "fix" something that wasn't broken.
I'll tell you... because in the long run I will make money by being more efficient with this new, higher level of web design that I can now offer.
Bottom line: Keep honing your skills and give your clients more than they ask for. They will return over and over again and you will earn more. Being a successful freelancer means that you can't rest on your past skills... you have to keep up and ahead of the curve. Invest your time in learning new skills. It will pay off in the satisfaction department and on your bottom line.