This is just me being nosey but what's up with houses up for sale but no listings showing on Realtor or Housesigma?

There are two listings around me, one I know is Re/max so it's not a sell yourself type thing and another I did not see the realtor company name so can't verify if it's private sale or not but they have both had for sale signs posted for awhile now (not coming soon) and I haven't seen them online.