Magic in a certain world works as follows:

• Elvish is the "language of magic", meaning all magic is chanted/invoked using Elvish
• To invoke the fire spell, the user must:

1. Chant "fire" in Elvish either out loud or in their head
2. Understand the meaning of "fire" in Elvish (you can't use it without knowing what "fire" means)
3. The user must also consciously want to invoke the spell

• Magic cannot be used without chanting either out loud or in one's head (so-called chantless) explicitly in Elvish. (any other language won't work)

The elves continue to use that language as their common to the modern day. However, humans and other species, are also capable of using Elvish (like any human can speak English, German, Russian, Chinese, etc) but still use their own common languages.

With the requirements to use spells, accidental casting (mainly by small children) should be a relatively small problem. The elves also use it as the common language without much problem.

In this world, magic is a must. One would find it very hard to survive without using magic.

Considering all that, in seems like Elvish should be the common language for everyone since:

• It would be easier to learn magic if Elvish is also the common language
• People in every country learn how to use magic regardless of social status
• Magic is an absolute must-know
• Anyone can learn Elvish (no biological differences significant enough to make one species unable to speak it)

What reasons may people in such a world have to decide to use languages other than Elvish as their common language?