Meanings of "Sumimasen" (すみません)
The article is in Japanese. It refers to an article from Chinese portal site Sohu (捜狐, http://www.sohu.com/ ) pointing out the difficulty of understanding nuances of the word “sumimasen” (すみません)
According to a survey conducted by the Japan Foundation in 2015, over 950,000 people in China are studying Japanese. In fact, any language school in Japan has more Chinese students than any other nationality and many Chinese people live and work in Japan, having full command of the Japanese language. Although they have advantages of knowing the kanji, the pronunciations are totally different and it must be of hard work that they are so fluent.
However, just like anyone who learns a foreign language, Chinese people also have a hard time learning the nuances of some words. Sumimasen is one example.
Usually すみません is taught as the word to express apology, which we Japanese actually use that way. For example, when you are running late for a meeting, you might want to call your client and say, すみません、遅れます (Sorry, I’m running late).
However, there are other uses of the word すみません and one is the opposite from the meaning in the textbook. It sometimes express gratitude! For example, when a waiter brings you a glass of water along with the oshibori (wet hand towel) at the restaurant minutes after you’re seated, you can say すみません instead of ありがとう (thank you).
Actually すみません is used more often than ありがとう when someone takes time or trouble to do something for you. Probably it includes the nuance of being sorry for having that someone take time for the humble me. Although ありがとう is more formal, すみません is not just a casual way of expressing gratitude.
Furthermore, すみません is also used like “excuse me”. “Excuse me, where is the train station?” will be 「すみません、駅はどこですか」. When the train is crowed but you have to get off, you ask the passengers to make way for you by saying 「すみません、降ります」 (Excuse me, I’m getting off). This can also be considered an act of humbleness.
So the word すみません includes the nuance of humbleness ingrained in the DNA (that’s an exaggeration of course ;-) )
You might want to check this article too (this one is in English):