Board Thread:Naruto Discussions/@comment-32900772-20170904113855/@comment-734582-20171012094016

Namikazenaruto9 wrote: If Absorption could solve that problem so easily why didn't kaguya use it? She knew everything their was to that seal. She was cautious enough to release them when she was absorbing their chakra... Maybe it can't, we don't know. But that wasn't my point. My point was, it was possible that Madara may absorb that ninjutsu. Without knowing the extent of their own power (they were still figuring it out), or the full extent of Madara's, they shouldn't risk a one-shot jutsu against a guy that may nullify it with ease. The intent of that attack was to restrain him first. That would make them capable of safely applying the seal and so defeating him. Just as Madara was underestimating their power (which is why he risked so much to obtained the second Rinnegan), they underestimated his.

The existence of the risk is enough. Kaguya was so powerful that nothing they did stuck anyway, and they had no hope of restraining her. Meaning they had no hope of trying to avoid the jutsu absorbtion and so simply had to try, it was the one shot they had.