Little investors get a list of funds and are told to do it themselves. We've tried a hundred ways to help people do this for themselves. But people aren't doing it. Even if you could teach this, most people wouldn't go back to rebalance their portfolios. There will be no sense of strategy that has been communicated to the participant.
People are binary - they're in one asset class or another.
Company stock is another problem. A lot of companies have a very strong stock culture. If you work for the company, you're supposed to own the stock. But every year, some company goes down and leaves its employees high and dry. Their job can be in danger and the stock will be down at the same time.