The uses you mention are common, but digital signage for advertising is big in retail. It's almost always trying to drive you to purchases.
Some network operators run 3rd party advertising to offset costs of running their network.
Also, if you see a sign at person level in a public space there's a high likelihood it's collecting demographics information on (age, gender, ethnicity - via video image processing) on everyone passing by while also trying to identity the mobile device in your pocket to geotag your advertising identity.
I work in a company that provides general interest "filler" type content for networks to display - news, weather, sports e.g.
Some network operators run 3rd party advertising to offset costs of running their network.
Also, if you see a sign at person level in a public space there's a high likelihood it's collecting demographics information on (age, gender, ethnicity - via video image processing) on everyone passing by while also trying to identity the mobile device in your pocket to geotag your advertising identity.
I work in a company that provides general interest "filler" type content for networks to display - news, weather, sports e.g.