why doesn't pip freeze > requirements.txt output Django?
Sounds like you are working in a virtual environment, yet your Django dependency is installed globally. Check which Python packages are installed globally and uninstall Django (you probably don't need it globally). Then install it into your virtual environment. Now the freeze command should output Django as well.
General note: Most packages should be installed into your project virtual environment. There are only few packages where it makes sense to install them globally (eg aws management tools).
I'm trying to deploy my Django site on Heroku, and thus, I need a requirements.txt file with the necessary packages that Heroku needs to install for me. I understand Django is a necessary package to be installed. Unfortunately, Django isn't included in the file when I run pip freeze > requirements.txt. Why is this? I'm not sure what to show you so you can tell me what's going wrong. Let me know and I'll add it. FYI the site hosts just fine on my local computer, so Django is definitely installed.