They do exist, at least in some places: https://www.att.com/home-phone/landline/

Long distance plans were a regulatory invention that allowed customers to opt out of the local phone company's long distance service. Today those companies don't make monopoly profits (because everyone uses mobile phones and VoIP) so they price their bundled services reasonably. This pretty much kills the market for stand alone long distance plans, although they do seem to exist still. No market, no advertising.