Use of ‘Por qué’ in this passage...

Question

Hola a todos,‘Da igual cuál sea tu sueño...’If I’m correct then I understand this sentence to mean, ‘It doesn’t matter what your dream is...’  The latter part of the sentence says, ‘it can be related to your lifestyle’. It’s the part of the sentence that says, ‘...no tiene por qué  estar relacionado con trabajo...’,  that I’m struggling with. I think I’m right to understand that it means, ‘it doesn’t have to be related with/to work’. I’m just not grasping the use of ‘por que’ here? Please could you explain it to me? Many thanks Clara :)

Answer

Hola Clara,
Yes, you got the right translation/meaning of this sentence:

..., no tiene por qué estar relacionado con trabajo,... 
(it doesn’t have to/ it doesn't need to be related with/to work)

the use of "por qué..." is a bit difficult to see, as it is an idiomatic expression.
In Spanish we use:
No tiene por qué + infinitive
to express that something doesn't need to be/have to be that way. Sometimes also "something shouldn't be that way.
It is always in negative (no tiene por qué...)
Here are more examples where you'll see it more clearly. I will give you a bit of context too.
1. Imagine you make a mistake at work and your boss starts shouting at you in front of your colleagues. Then you say to your boss:

Usted no tiene por qué gritarme así en medio de la oficina.
You shouldn't/don't need to shout at me like that in the middle of the office.

2. You go to a camera shop and ask if the low price of a camera you've seen on the window means that it is bad quality. Then the assistant says:

No, esa cámara no tiene por qué ser de mala calidad por el hecho de ser barata.
No, that camera doesn't need to be a bad quality one because of the low price.

3. Everybody at work is collecting money for a colleague who is leaving after 3 years working there, but you started to work there 2 weeks ago, so you don't really know that person well. One nice colleague goes to your desk and says to you:

Clara, tú no tienes por qué poner dinero. No te sientas obligada.
Clara, you don't need to give any money. Don't feel you have to.

4. Your boyfriend is telling you he doesn't want to continue with your relationship. Things haven't been great lately. You are more positive about the relationship and say:

Esto no tiene por qué ser el fin de nuestra relación. Todas las parejas tienen problemas de vez en cuando.
This doesn't have to be the end of our relationship. All couples have problems now and then.

I hope this clarified it for you.
Un saludo y buen "finde"
Inma

Answer

¡Oh Inma muchísimas gracias por tu explicaciones!Ahora lo tengo...justo. I think I’ll need to practice this a lot, haha. :)Igualmente, saludos y que tengas un buen finde!Clara