She knew from a young age that her sole 'purpose' (in life) was to be a writer. [=she knew that all she wanted (in life) was to be a writer]
We were happy to know that the money was being used 'for a good purpose'. [=for something useful, important, etc.]
There's little/no 'purpose' in restarting the process. [=there is little/no reason to start the process again]
(..) I've completed doing... ...what I swore an oath to God, years ago, ...to never do again. I have created "something that kills people." And in that purpose, was a success. I've done this because philosophically, I am sympathetic to your aim. I can tell you with no ego, this is my finest sword. (..)2003 Kill Bill: Vol. 1