Your visitors will leave very quickly if your site is slow or unappealing.
In the modern age of the internet a website is your virtual business face, if its not pleasing to the eye or slow and hard to navigate visitors will leave , even worse they will go to one of your competitors to do business.
We also build sites that will show well in Google and not just look pretty. Many web site designers only deal with making a site look great. How many times have you heard of someone having a beautiful made only to not really get many customers from it.