Probably because we don't realize that it's harmful (by design, or by accident). Second, it's not 'a device', it could be the algorithm behind a seemingly helpf

Probably because we don't realize that it's harmful (by design, or by accident). Second, it's not 'a device', it could be the algorithm behind a seemingly helpful service, like Google search. Third, maybe it's used as a weapon against 'other people' (most likely).