When people give something to a memorial/remembrance venue, they feel like they are involved and a part of it. It is also then a special place for them to go where they can view something they may have at home in a more reverent or feel-good way. This is why family members visit pictures of their deceased family members when they put them at a remembrance/memorial. Same with tombstones. You may walk past a picture of a deceased family member every day, but visit people will visit that same picture if it is somewhere else and in a reverent location to "talk" to them.