"purpose for why" is a correct and usable phrase in written English.
You can use it when you are asking why something is done, or for what purpose something is done. For example, "The doctor has not yet revealed the purpose for why he prescribed the medication."
The answer is probably neither, and the exact behaviour is probably very different for different individuals and different purposes for why multiple aliases are used in the first place.
This is one of the main purposes for why people travel.
"If it was a true, unrestricted gift from Seth Rubenstein to Nora Anderson that she could use for any purpose, then why can't she use it for her campaign?" he said.
The yearning for purpose — the why — is as valid as curiosity about the process — the how.
This is a serious matter that merits a complete investigation, and we demand to know who looked at Senator Obama's passport file, for what purpose, and why it took so long for them to reveal this security breach".
It means finding a higher purpose -- a greater reason for why we get up and go to work each day -- something more than just increasing our piles of possessions and power.
Their astringent demeanor is all that is necessary to broadcast their purpose for being who they are, why they are, where they are.
"If we weren't teaching grammar as a way to bring the voices of our students forward, for a redemptive purpose, then why teach, why live?" she said.
If such a human being can rightfully be destroyed for this purpose, why not a human being at any other stage of his or her existence?
Lord Marland admitted that the existing Mox plant is not fit for purpose, which is why the Nuclear Decommissioning Authority has brought in the French nuclear company Areva, which wants to build the second Mox plant based on its own Mox operation at Marcoule in the south of France.
