Why Not?

When he read that the Mancer Scape was virtual, he was somewhat disappointed. After all, he thought he needed to kill real creatures in order for his Quest rewards to trigger. 

But this wasn't the same. 

Although it was known as a "virtual" world, the Mancer Scape used very real Blood Essence. One would truly lose their lives if they weren't careful. 

One of the reasons the Mancer Scape was so valuable was because its Rune Laws were incredibly unique and functioned very similarly to the Split Realm Dungeon Sylas had just been in. 

When you killed a creature inside, their Mature Aether would come to you just the same, but this wasn't all. You would also naturally gain their Blood Essence. 

This world was so invaluable because it was a shortcut to improving one's affinity. If you targeted beasts of your own Path of the Mancer, you could increase your affinity by leaps and bounds, not to mention lay a foundation for future Grades.