Why would people greet me in Mandarin, not in English?

I don’t know if you have noticed it, it is very common to see people working in the airports or in any form of tourism in major cities to greet East-Asian-look-alike in Mandarin.
“你好Hello”, “謝謝Thank you”, “再見Goodbye” in Mandarin.
But that’s the only three words they could say in Mandarin. After “你好”, they switched to English mode again, and after the conversation, they use “謝謝” or “再見”.
What’s that for?
(In the past, they just greeted me in English and have conversations with me in English.)

It’s not even a way to be nice, in my opinion.

They greet all East-Asian-look-alike in Mandarin, which means that they see all East-Asian-look-alike as the same group of people.
People all around the world know damn well that the U.K., France, and Germany are three completely different countries with different cultures and languages, but they don’t understand there’re also non-Mandarin speaking countries (i.e., Japan, Korea, and Mongolia) in East Asia?

How could they tell if a person speaks Mandarin by simply looking at him/her?
When I was in the Japanese neighborhood in Taipei City, I couldn’t tell who are Japanese and who are Taiwanese/Chinese.
By the same token, a French/German can’t really tell if a person is from France or from Germany by simply looking at them.
If they are neighboring countries, people move around or have cross-national marriage, so there’s no way that you can tell their nationality by simply looking at them.

East Asian people may speak English to all Westerners, but that’s because English is the current Lingua franca of the world, not because they think all Westerners are from the U.K., the U.S. Canada, etc.
Westerners greet all East Asians in Mandarin, and that’s because they think all East Asians are Chinese from China.
See the difference now?

Greeting all East-Asian-look-alike in Mandarin is just a way to be nice? Who would come up with such an idea to single out a certain group of people?
What about greeting all Middle-Eastern-look-alike in Arabic?
What about greeting all South-Asian-look-alike in Hindi?
What about greeting all African-look-alike in Igbo?
The list seems to be more and more inappropriate, right?

I know it’s difficult for native English-speakers to relate to such situations.
Because your native language happens to be the current Lingua franca of the world.
Just imagine that you’re in Taiwan and you speak Mandarin or Taiwanese perfectly, but Taiwanese people keep considering you French (but you’re not), speaking French to you (but you don’t speak French at all), and making comments about France or the French behind your back.
That’s probably how it feels like.

P.S.
Okay, the point is, they shouldn’t assume others’ nationality or ethnicity, especially when they can’t really tell the difference.
(Unless they have checked others’ passports and know exactly what their nationality and ethnicity is.)
Jesus Christ, the problem is so obvious, yet all of you just want to trivialize it.
They mistake non-Chinese(Japanese and Koreans) for Chinese, and therefore greet Japanese and Koreans with “你好”. That’s inappropriate!
What about they start greeting Indian Sikhs with Arabic language or Islamic etiquette and manners? That’s inappropriate!
What about they start greeting Western people of African descent in African languages? That’s inappropriate!
If it was the Indian Sikhs or Africans who got mistaken, will you still want to trivialize it?

32 posts were merged into an existing topic: First time to the U.K. Strange and unexpected impression.