User blog comment:SomeoneYouUsedToKnow/SYUTK's V4E10 - Guroyuri - Impressions/Recap/@comment-25405817-20170124025735/@comment-25405817-20170125025121

1) Why waste time and energy to level something that will eventually crumble by itself? Grimm being able to learn helps them figure those simple things out.

2) It is still shelter, and it isn't brimming with monsters. For a couple of travelers carrying a living fossil, it is still pretty safe than out of the village. They just didn't count on the Nucklelavee being around, waiting for new people to arrive.

Those are pretty simple explanations. Anyone who isn't antagonizing by nature could see the reason in them.