Responsive design needs lots of it! We can no longer call what we do web design as websites move more and more towards applications.
A good web designer and developer will not only build a responsive website but will make sure it works across a range of browsers and a range of devices. To do that effectively we need to have access to actual devices.
No developer should ever underestimate the time and investment that goes into training and keeping up with new technology. Equally the financial investment into devices for testing is not to be sniffed at.
This photo is a bit over the top from the Techcrunch website but does indicate the testing environment and that is just Android!