That is not the fact. Here in the Bhāgavata says the Purāṇa is part of the Vedas. As Upaniṣad is part of Vedas... It is written in simplified language so that those who are less educated, less having brain substance...
Now, this Mahābhārata is especially written... Mahābhārata. Mahābhārata means the history of greater India. Mahā. Mahā means greater. Bhārata. Bhārata means India, Bhārata-varṣa. Mahābhārata, greater India. Or at that time the whole world was Bhārata-varṣa. Therefore greater India, history in Mahābhārata is there. So Mahābhārata especially was written for three classes of men. What are those? Strī, śūdra, dvija-bandhu. Strī means woman, śūdra means worker class, and dvija-bandhu means persons who have taken their birth in higher caste, brāhmaṇa, kṣatriya, vaiśya, but they're degraded. They could not keep up their standard of culture. Just like at the present moment. They are introducing themself as brāhmaṇa, but degraded.