Okay, finally I understood what was happening and I didn't realize. On one hand, virtual environments are completely independent from the global or system, so what is being installed in one side it shouldn't affect the other. On the other hand, what happened was, that for being inside the Scripts folder, when trying to execute Python commands I was actually executing the scripts with the same name, which are copies to use with the virtual environment and which can be used calling the "activate" script. There was actually no problem, it was me messed up.
Thanks to all contributors for their help.
After learning how to code Python I'm starting to learn and figure out how to structure projects and set virtual environments up, but I can't make my mind up on how are packages managed when the virtual environment is activated. To make an example: I want to make a Django project. So, first of all, mkdir the project folder, cd into it and then execute python -m venv [whatever]. cd into Scripts folder and execute 'activate'. Then, pip install Django and pip list and shows Django. At last, I deactivate the virtual environment and make pip list again. Why is Django listed there? Should it?
How does pip work under virtual environments?