Stick To Wordpress Or Move To Squarespcae

OK, I have just been introduced to a site called Squarespace. I dont know much about it, but what I do know is that it si similar to Wordpress. The immediate visible difference is that you have to pay (on a monthly basis). Yes, I know that Wordpress is free, however, is there any reason why Squarespace charges and Wordpress doesnt? For those of you out there already using Squarespace, and have used Wordpress before, kindly fill me in on what the difference is.