User blog comment:Sargenttacos115/Why are Sting and Rouge so weak?/@comment-74.194.216.147-20131110235054/@comment-7418318-20131111165357

Lacrima are physical objects.

On the asumption that Dragon Slayer Lacrima are like "regular" Lacrima, they are a kind of crystal.

And juding from what Makarov and Ivan said, they have to be implanted (or explanted) via surgery, so they couldn't just be absorbed like that.