‘Mum, why would you say a thing like that?’ Is this the same as ‘Why do you say a thing like that?’
‘Why would she make our lives such a misery?’ The meaning was clearly: ‘Why is she making our lives such a misery?’
The use of ‘would’ in your sentences introduces the idea of incredulity. What I mean is that the speaker can’t really believe/accept what the other person is saying.
Example -
Why would you go by car when it’s quicker to walk there? In other wods I can’t really believe that you would do that.
Why do you go by car when it’s quicker to walk there? This is a straightforward question without any hidden meaning. Preformatted text