Transferring Parasite
Back then, grinding like this was impossible. Getting exp and points at the same time was hard.
If he grinds like this, he would get a lot of exp to level up, but he wouldn't get any skill points as he didn't accept any quests. Yes, his level would easily increase this way, but the level of his spells, combat arts, and class would stop increasing.
This was the reason why players had to complete quests to get skill points, free attribute points, cards, and titles. Or else they would simply farm and kill every creature that they saw to increase their level, even if it was human or demi.
In quests, players didn't care about the exp that they would receive as there were various ways to get exp. Just by killing thousands of creatures, they would surpass the amount of exp that they get from completing a quest that will take a week to finish.