From the FAQ, it seems they also picked a Lagrange point in order to block out all light from the Sun, Moon, and Earth, which will help stabilize the temperature (necessary for infrared observations).
It does seem like a brutal and somewhat questionable tradeoff though, to send up a telescope that will only last 10 years and cannot be serviced, versus Hubble which has been going strong (with repairs and upgrades) for 26 years.
The wait for the JWT has been excruciating, and we still have two years of testing left before launch. We are fortunate that Hubble has continued to work reliably since its last service mission.