Problem or not, the back and sides of any tank should be covered with opaque material to make them more secure for the snakes. A lot of people can think that they don't have to do this for adult snakes, since they 'don't react badly and don't stress', but adults don't tend to show stress the same way little ones do. Better to play it safe and just cover the tanks.

Also, unless in a very warm climate, the back and sides of tanks should be insulated as well, lest the temperatures fluctuate too much. Glass is a terrible heat keeper on its own.