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Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why are Hindi and Urdu considered different languages, and not dialects of the same language?

From what I can tell, most native speakers of one language can understand the other, and they share most words/grammar structures. Why are they separate languages and not dialects?
gpt
depends on who you're talking to. a linguist would tell you that they are not even dialects, but registers of the same language (hindustani). they're correct: hindi and urdu are mutually intelligible with the main differences being vocabulary. 

urdu takes a lot of vocabulary from persian and arabic due to the influence of muslim leaders. hindi, however, has decided to replace this vocabulary with words coming from sanskrit.

politics play a huge role in the hindi-urdu split: urdu being the language of pakistan (despite the fact that most pakistanis speak punjabi natively, and urdu for most is a second language acquired in school) and hindi being the language of india (despite the fact that india is one of the most linguistically diverse places in the world, and english being one of the mainly used languages in education and commerce). in the last century, india and pakistan have grown to have separate identities due to religious and political reasons.

also, many hindi speakers cannot read the urdu script, and vice versa. not because they can't learn, but because they simply never did. so, in a place like canada where a lot of people speak either language, it makes sense to have one message in hindi and one message in urdu.

keep in mind that both hindi and urdu have standard forms, often taught in schools. however, people don't tend to speak standard hindi or standard urdu; instead, they will speak their own regional variant of this hindustani language. in writing, however, the standardized forms are quite common.