“没必要” is more than just a phrase; it's a reflection of a deeply ingrained cultural value of pragmatism (实用主义, shíyòng zhǔyì). In many aspects of Chinese life, there is a strong emphasis on avoiding waste (浪费, làngfèi)—whether it's wasting time, energy, money, or resources. “没必要” is the verbal embodiment of this principle. For instance, in Western cultures, one might perform an action for the sake of politeness or principle, even if it's inefficient. For example, repeatedly offering to pay for a meal after being turned down. In a Chinese context, after one or two offers, continuing to insist might be seen as “没必要” because the decision has been made. This phrase can also be a tool for maintaining social harmony and saving face. By saying “哎呀,没必要这么客气!” (Āiyā, méi bì yào zhème kèqi! - “Oh, there's no need to be so polite!”), you can gently refuse an overly generous gift or favor. This relieves the other person of their obligation while showing your own humility, preventing the situation from becoming awkward. It's a soft but clear way of saying, “Your kind thought is enough; the action itself is unnecessary.”
“没必要” is incredibly common in daily conversation, from casual chats to business discussions. Its meaning can shift slightly based on the context and tone.