Explanation:

The ancient sages had the divine ability to take the correct meaning of the word Brahman as per the context. Therefore, there was no confusion in the case of the sages and hence, the same word Brahman was used to mean both God and other ‘greatest’ worldly items. According to the context in the Veda, the sages would accurately select either God or the relevant worldly item as the right meaning of the word Brahman. Hence, there was no necessity of using a separate word like Parabrahman for God. But today, human beings do not have such a divine ability due to the fall in their standards. Hence, there is a real need for introducing an isolated word i.e., Parabrahman, which is restricted to mean God alone.

[1] Differing and contradicting views about Brahman.