Knowing cultivators, he expected that they wouldn't like being used as a breeding ground. He was a clear example of what to expect.
So, if he didn't want a repeat of his resentment towards the person using him as a breeding stock appearing in his disciples, it was of utmost importance that Dao Fetus be viewed as powerful and helpful symbiotes. At the very least, he had to render the normal cultivation system obsolete and make it so that the ones who refused to convert to his cultivation system would be slowly wiped out until they became extinct complete.
The only way he knew to accomplish his nefarious goals with the Dao Fetus cultivation system was to make it immensely powerful. Therefore, the energy requirements would reach 31 times at Rank 5.
He could offset the energy cost by providing it himself, but he chose the less expensive method of reducing the burden with the size of the Energy Well.
