This is because the expense ratio of a Regular mutual fund plan is almost three times higher than corresponding Direct mutual fund plan for the financial year 2015 - 16. (wealthtrust.in)
There are no charges of any sort for investing in Direct mutual funds. (groww.in)
In the race to get higher returns, it could be disastrous if you invest in a wrong Direct mutual fund scheme and make say 10 % lower returns than its fund category. (relakhs.com)