While surprise is a universal emotion, the frequent and formulaic use of `没想到` highlights a common conversational pattern in Chinese. It's often used as a discourse marker to signal to the listener that a surprising piece of information is coming. This helps manage the flow of a story and builds a little bit of suspense. For example, in English, we might say, “I went to the store, and you'll never guess who I saw!” The phrase “you'll never guess” serves a similar function to `没想到`. However, in Chinese, `没想到` is more integrated and frequently used to frame an entire clause: `我以为他今天不回来，没想到他下午就到家了` (Wǒ yǐwéi tā jīntiān bù huílái, méi xiǎng dào tā xiàwǔ jiù dàojiā le) — “I thought he wasn't coming back today, [but] unexpectedly, he got home in the afternoon.” This structure, which presents the expectation first and then immediately contrasts it with the unexpected reality using `没想到`, is a very natural and rhythmic way of storytelling in Mandarin. It's less about a deep philosophical value and more about a pragmatic, everyday communication style.
`没想到` is extremely common in spoken Chinese and informal writing. It's versatile and can be used in almost any situation where reality defies your expectations.