Numbers count, as does linguistic unity:
14. Since the introduction of languages into liturgical use by the Church may actually affect the development of the language itself and may even be determinative in its regard, care is to be taken to promote those languages which – even while perhaps lacking a long literary tradition – seem capable of being employed by a greater number of persons. It is necessary to avoid any fragmentation of dialects, especially at the moment when a given dialect may be passing from spoken to written form. Instead, care should be taken to foster and to develop forms of speech that are common to human communities.
I don’t know if this concern about “dialects” is as notable in English developments as its huge capacity for adopting new words. But perhaps other commenters have an experience with dialects of English or other languages.
