Analog ads have an installation & maintenance cost associated with them. Digital ads don't - if you have a screen anywhere, it can be turned into an ad with little effort and will require no ongoing maintenance.

Exactly. Ads are basically pollution. Digital (and network-connected) ads drive the cost of polluting to near zero, so you see them everywhere: on transit, in gas stations, on your TV's UI, in your operating system, etc. Analog ads actually have a deployment cost, so they don't pollute the space as much.