It's your choice; there is no "must". Yes, licensing your work with a fully free license like BSD means other people can profit off your work, but so does publishing your work in an academic journal. Copyleft licenses like GPL do nothing to prevent others from using your work to draw conclusions or without distribution to make a profit, either (though CC Share-Alike licenses do). You should also recognise that the likelihood of someone taking academic code and actually using it in something else is often (it depends on the field) very slim.
I was surprised by the fediverse obsession with copyleft and insisting that all projects ought to use it otherwise they're traitors to open source and themselves.