It definitely does, but the magnitude of the affect varies based on the clientele. For example, the affect on a web-based business would probably be much greater.
For example - I ran a file hosting site a number of years ago using a pre-built php script, and the default template with a few modifications. I ran it with this template for a few years, until I was making enough profit to warrant hiring someone to make a new site template for me. I hired someone off of rent-a-coder for less than $100, and within a week of installing the new theme my pageviews increased about 20% overnight, and stayed there.
For example - I ran a file hosting site a number of years ago using a pre-built php script, and the default template with a few modifications. I ran it with this template for a few years, until I was making enough profit to warrant hiring someone to make a new site template for me. I hired someone off of rent-a-coder for less than $100, and within a week of installing the new theme my pageviews increased about 20% overnight, and stayed there.