Who cares what its purpose is, the test doesn't work. It could have any purpose and it would be irrelevant if it doesn't achieve that purpose. You talk as if the Turing Test is some kind of immutable law of the universe enshrined beside e=mc^2. In reality it's just a faulty mind game devised by someone who couldn't have begun to dream of the sophistication modern programming would achieve, no one takes it seriously.

For the record though, the Turing Test was a flawed and heavily criticized method of attempting to determine if a machine can think, developed by Alan Turing when computers were the size of entire rooms. Its purpose is irrelevant since the method and premise of the test is flawed and ineffective.