Just catching up here, but perhaps you would like to explain that remark?
From a casual reader's take, it might stink to high heaven, like soneone destroying evidence. So you might explain why these whackos would just up and destroy hard drives if it is not "really" unusual?
Well, given that Dylan and Eric offed themselves at the conclusion of their massacre, one may legitimately doubt they gave a damn about the altitude of the stink resulting from their having destroyed evidence. After all, they destroyed a lot more than evidence that day — including, thankfully, themselves.
Perhaps they worried that stuff in their digital lives would conflict with the "legacy" they intended to leave. More likely, however, is that they just wanted to leave investigators with a tougher puzzle and conspiracy theorists with more unknowns on which to base crackpot theories.