It's not a problem, if you have an alternative plan. Like, if you decide, that traditional education/job is not for you, because you want to be an artist/musician/travel the world/save stray kittens/whatever, but you DO actually know, what this purpose of your life is. The real issue is, that there are people, who have no plans and goals AT ALL and their answer to this question is something along the lines of "just existing", "just getting by", "just trying to survive". Work and formal education doesn't have to be the purpose of life, but life should have a purpose beyond day to day existence.