The expression ¿Qué necesidad? works for communicating that what someone thinks is necessary really isn’t. It can used alone or with a clausal complement. Let’s look at some examples:
- Pero ¿qué necesidad? What do you need this guy for? He’s a jerk. He treats you badly. You can do better than him. You don’t have to suffer like this.
- ¿Qué necesidad hay de decírselo? What is the point of telling her? What would be the point of telling her? The speaker is suggesting that there is no point.
It’s commonly used when the speaker is frustrated with the other person’s inability to see the situation as it is. You can also use it to refer to yourself:
- Pero, ¿qué necesidad? But what do I need to get married for? What’s the rush? (overheard at a wedding)
- ¿Qué necesidad tengo de estar escuchándolo? Why should I put up with listening to him? It’s not a requirement. I don’t have to.
As this last example shows, have to put up with (someone or something) is often a good translation.