People that have cars listed for sale probably won't ship. You would have to make arrangements with a transport company. Cargurus doesn't sell cars, people and dealers list them on this site to sell. This part of Cargurus is a forum for people with car problems seeking help from people who know how to fix the problems.
Most sellers aren't paying for shipping is my guess. Which means, of course, that if you buy a car across the country, you're in at least another $1,000 or so before it's actually "yours." I sometimes buy & flip cars from other parts of the U.S. and I use A-1 Auto Transport when I do. They're cheap, reliable and get the job done on time, which are my biggest concerns.