Plenty people would absolutely grab a folded-in-half iPad out of the trash. Scavenging parts for one (eg, a flash chip...).

The drilling in this case is to destroy data, not to stop someone investigating.

There can be great legitimate reasons to wish to do so, for example, a lawyer, journalist or doctor wishing to preserve innocent persons privacy. The reason doesn't have to always be nefarious as you maybe are imagining it to be.