Use of the LESS environment variable?

In step 9 of the Lingua Franca project, we learn that the less command can be configured through the LESS environment variable. It seems that by setting this environment variable, an option of choice is passed to less automatically every time we call it.

  1. As we also learned to create aliases for commands, I wonder what is the use of setting the LESS environment variable instead of just creating an alias like lesn="less -N"?

  2. Are there any other commands that can be configured in a similar way using (corresponding) environment variables?