system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are boogers and ear wax two seperate things when they have the same purpose?
gpt
Lets say you have two classes of students, and you give them the same problem to solve- how to clean a chalk board. One class is sent to the library, and the other to the auditorium. 

The class in the library learns that they can take all of the books and fan the dust off of the board.

The class in the auditorium learns that the curtains can be used to wipe the board clean.

Now, lets say you ask these classes the same problem again the next day.

Each one now knows a way that works to do this, and will just repeat it like they had before- the books are still laying out in the library and curtain is pulled up to the board in the auditorium. They quickly solve it using the same method, maybe adding a small change but mostly just using what works and is already available. 

The classes can't just tell the other "Hey, just use the curtain!" or "Use all of the books as fans!", because what works in a library might not be doable in the auditorium, even if they're solving the same problem.

This is similar to how different pieces of your body developed over millions of years. 

Ear wax is the product of millions of generations of solving this problem one way, as are the parts of your ear that make and regulate it- the same goes for your nose's snot, which solves the problem another way.