'You'll benefit from the course if your ELO rating is at least 900' and 'This course is designed for players who know the fundamentals of chess. They have an ELO rating somewhere in range of 800-1500.'
Edit: I am asking why people do things in a certain way. why opinion based? sounds pretty factual to me: I'm not asking what should be the case. I'm asking why certain things are the way they are.
People simply don't recognize Elo as being a last name; it's Hungarian, which is completely unrelated to English. People do recognize ELO as a rock band so it's not strange to think of it as an abbreviation, especially since some kind of chess ratings (FIDE rating, USCF rating) are capitalized. I guess this happens with many three and four letter words, so that explains why you never see GLICKO. That is just more recognizable as a proper name.