>Suppose you sell insulation and replacing the insulation in an existing house could save $2 in heating and cooling for each $1 the insulation costs. Most people know that insulation exists, but what causes them to realize that they should be in the market for it when they "already have it"?

The same legit things that can cause them to realize it today. Word of mouth, a product review, a personal search that landed them on a new company website, a curated catalog (as long as those things are not selling their placements).

An ad is the worse thing to find such things out - the huge majority ranges from misleading to criminally misleading to bullshit.