Messages which require online action work better in email than DM (direct message on social media), whereas calls-to-action to text to a shortcode or download a mobile app work fine within a DM. RFM and response analysis will indicate channel preference since customers with a preference for specific online channels will be more responsive in them and will make more purchases online.
That isn’t to say that sales-y promotions couldn’t ever create results—as marketing “gurus” have proved. The results just aren’t as good as they could be. Take the biggest gurus’ results—the ones they boast about—and calculate their conversion rates. Often their marketing is comparatively ineffective. They just have massive volume, so the sales numbers are impressive.