Look at Arabic; one "language" despite being barely mutually intelligible between, say, Iraq and Morocco.
Ie same way that people in Luxemburg want to point out that they have their own language different from German, rulers of Morocco (who are Arabs - majority of Morocco's population native language is Berber) want to stress that they share same language & culture with rest of the Arab world.
In other words - if you are a country, you have the option to have your own language (even if it's mutually intelligible with a major other language). If you are just a part of a country, that option seems off the table (ie you need a non-mutually intelligible language to make that claim).
[1] http://matadornetwork.com/abroad/why-hindi-urdu-is-one-langu...