Does your operating system not allow you to rename downloaded files?

I guess I mean more that there doesn't seem to be an agreed upon convention that people actively use so that I don't have to manually rename things

(otherwise I wouldn't have to ask a question about this topic if files I download had some title you'd easily find in a search through files)

and I was wondering if we should encourage people to utilize a certain filename convention or if existing lack of a convention has a purpose

(programming languages for example sometimes have "style conventions" for how code should look; likewise I guess this is a kind of question about a convention about naming files - intuitively I'd think a PDF file of a book on "Geology 101" should be named "Geology101Book.pdf" for example, but frequently I do not encounter this)