Why are they a big problem about landmines?

Question

Why are they a big problem about landmines?

Answer 1

uhh...if you step on them they blow you up...

Answer 2

They can planted in large quantities, the record keeping of their positions is typically not very reliable, and their purpose involves them being difficult to notice until you tread on one.  Oh, and they stay effective for years.

They tend to get laid on open countryside, and that was and will be agricultural land.  After the war, a farmer goes out to plant an area of land and comes back with one leg less than he left home with.  A child finds an interesting looking something or other, and gets killed or crippled for life.

Those are big problems, and they can occur decades after peace was declared.  Regardless of the possible presence of landmines, that land has to be ploughed and sown because the local people need to eat.