I wonder who and why decided that downloading files from the internets into a fixed location is a good idea? A downloaded file may be a PDF document, installer

I wonder who and why decided that downloading files from the internets into a fixed location is a good idea? A downloaded file may be a PDF document, installer of a software, a song, a photo, CAD file, anything at all. Makes no sense to save everything into a same location. Hierarchical file systems were invented for a reason. For the same reason, I want browsers and chat apps to ask me where to save each file I download. Fortunately, most of these apps have an option to enable such behavior. As a nice side effects, this prevents security issues like the one described in the article.