I don't know how old you are or in what geographical location you grew up in, but in my elementary school in the Midwest US, we were taught about the five senses. It was left at that. In high school biology, we were taught that everything we learned in elementary was wrong, simplified so it could be taught to hold our attention (a difficult chore with children).

This is where my teacher told us that we had more senses. Sense of pain. Sense of balance. Sense of electricity. I accept that there are more things that can be called senses. I also accept that there may be reason to teach them. However, there are a lot of things taught in schools, and a lot of things that are not. The concept of sense is important to know, but so are a lot of things. My school taught that there may be more senses, so I guess I might be confused by the notion of any educated person not knowing other senses exist. As a simple teaching method (keeping in mind public schools are mandatory and therefor must keep the students attention), "five senses" as an example works for children, and as a turn of phrase for adults. It's up to the educated mind to continue learning, and this is where schools fail.

Teach fact. Teach how to find these facts. Only get into the detail when there is something to be gained. Anything else and you risk losing your student. Like I said originally, people "know" there are more than five senses. The phrase sticks because that's what we learn as a child.