Why don't we know the names of the American hostages in Gaza?

[ArMaP]

Apparently nobody knows the names of the hostages, except those whose families know they are missing and assuming they are hostages.
Some days ago I saw on Euronews people on a demonstration (I think it was in France) complaining that they do not know the names of the hostages, so they do not know what happened to their missing family members.