Of course, besides the materials being easy to gather, there was another very important reason. [God-Stealer] was different from the power obtained through other rituals. In a sense, it was even safer than transaction rituals.
Because the core of this ability is "stealing," while the core of transaction rituals is "picking up."
"Stealing," naturally, means to take something silently, without anyone knowing a thing. Unless you expose yourself, not even the original owner will find out. Naturally, the connection is severed completely.
But "picking up" is different. Even if it's something that was clearly abandoned, there are always some non-human existences trying to exploit a loophole on Isaac, forcibly claiming the item as Theirs.
Therefore, with the power obtained using [God-Stealer], there's no need to worry about being usurped, unlike with other methods.
So, even repeatedly stealing the power of a specific Outer God wouldn't have any major repercussions.
