The concept of 'humanitarian mine clearance' - where an entire area is completely demined in order to rehabilitate it - as opposed to 'military mine clearance', with its more limited objectives, is a post-Cold War notion. As such, existing technology is both primitive and inadequately designed when it comes to meeting the expanded needs and pressures of humanitarian clearance.
Humanitarian clearance is essentially about clearing up the 'war junk' left behind after any armed conflict. To clear any site, be it farmland, road, or urban area, every inch of ground must be carefully probed by hand and guaranteed to be mine-free, before it can be returned to the community. For safety reasons, mines destroyed in-situ, rather than being lifted. This also removes the possibility of the mines being sold for re-deployment elsewhere.