Chants come from the author thinking they're cool and mystical, and creating an in-universe reason to justify it. And then other authors were like, how about if people in my setting also chanted but my MC was special and had no weaknesses, so they decided that, for example, actually chanting is a crutch that makes you bad at magic and my MC's too smart or special to have weaknesses.
Same applies to skimpy outfits, or people good at magic being bad at fitness, or just specialization in general.
Anyways, as for the OP, imo made up languages leave more to the imagination, and give the impression of being more difficult for people to learn/understand in-universe than if it was just normal language.