2. It’s a sign of respect and creates instant connections.
Even if someone speaks your language, to arrive in their country and assume they wish to speak it to you is slightly ignorant. This is one of the reasons that Anglophones are infamous for being so rude abroad, the majority of them don’t make any effort to speak anything other than English. Even attempting a few words when in a shop or asking for directions shows that you have had enough respect to at least try. I have found that speaking someone’s mother tongue to them creates instant friendships as well because they feel more comfortable around you when they can be themselves.
3. A lot of things are “lost in translation”.
If you have ever read a translation in your native language that has been translated from another language and the looked at the original, you will know this. Some of the translations are very embarrassing! There are a lot of idiomatic phrases that cannot be translated because they only make sense in that language. Things like humour and play on words can also only be appreciated in the original language.