Why would we change the value of a variable rather than create a new variable? I can understand if the variable is defined by something happening in real-time. Like a temperature reading. In the course it is not clear why and what the purpose would be to simply change “lunch” to something else.
Sorry this is a late answer.
The reason behind this isn’t really evident yet in the course but becomes valuable when you begin learning functions and loops. This gives the opportunity for a function to always print the variable even if it gets changed throughout your code, or for a function to regularly change a variable then print it.
It can also be valuable to keep the number of variables lower so your program can run more efficiently. Something more relevant when your code becomes long and complex. Both of these should make more sense later on.