Why is the PS1 being called the PSX?

Well, seing as the PSX has the PS1 and PS2 in it, why not call it the PSX. After all, it was never called the PS1 in the first place. It was just PlayStation. To say PlayStation now to someone, they would be like, which one? You know what I mean? So just call it the PSX so people know what you are talking about.