Well spotted, I've never been asked about this before.
The short answer to that one is yes, it would be beneficial.
The long answer is that archival standards recommend storing media in a controlled environment, and that relates to temperature, humidity, and even providing a clean air environment.
It's a bit excessive to expect normal domestic users to adhere rigidly to the ultra strict archival standards however anything that assists with any of these factors will be beneficial to some degree.
Even if the container isn't airtight it still limits the flow of air over the disc and therefore exposure to atmospheric contaminants. The container also acts as a buffer to changing temperatures and humidity.
Every time you open the container you expose the disc to fresh contaminants so discs are best kept in the container until use. An airtight container would lessen the exposure but the discs would of course still be exposed to fresh contamination every time the container is opened.
If you're storing discs long term then removing any paper inserts is also recommended as these attract moisture which then increases the relative humidity surrounding the disc.
At a practical level however all of this simply means that if you leave a disc lying around exposed to light, humidity, temperature variation, and atmospheric contamination, then the disc won't last as long as it would have otherwise. The degree of this is almost impossible to quantify though as there are so many interacting and interdependant factors that apply.