Currently, new users who may not be very familiar with a shell environment can easily find themselves in a mongo shell, such as verifying they've correctly added it to their path. Then, they may not exit the mongo shell but instead try to launch a new shell or connect to a database. This results in the following errors.
There are currently 22 threads in Education's new forums that show users encountering this situation, and countless more in our old forums. Adding a default to shellHelper would help ameliorate this and provide better feedback to our newer users.