Ah, all along the seemingly consistent order of available languages on the bottom of each page depends on hand sorting them in the source of each page.
Let's imagine it is the year 2050 and each article has been translated into each language. A simple misplaced language would e.g., cause ZH users, who are used to looking for their language at the bottom, to not find it.
Also some authors might think, "ZH is the worlds most populous language, it belongs on the top!" So to prevent anarchy consider some standard sort automatically implemented. OK, enough FUD from me today, bye.