Duty in Service
Some clients believe value is intangible in the short term and encourage audience to invest in them on a contractual basis or for longer terms. Industries like this usually delve in B2B spaces but employ social media as a tool to widen their reach and reshape their customer base.
Self-referential
Ads for the digital marketing agency I was in also involved coming from a businessman / salesperson approach. Speaking through the eye of the potential client, when writing for a digital marketing firm acquiring business.
As a new firm, there was less focus on branding and more on expanding businesses' methodologies against customer's pre-conceived system of working.
Space for knowledge
A way to provide relevance in a service space is accessibility to free knowledge.
This is common today through advertiser's free webinars / masterclass trailers / one time consultation. In the case of the agency I was in, Email was a chosen expression to build longer subscription potential.
List is not limited to the ones shown and expandable over time.