Small venues that host stand-ups or art shows or pop-ups, get whatsapp numbers of visitors to promote future shows. I am a part of one that uses the WhatsApp channel feature for this (Of course this is in addition to FB/insta posts)

I know a few instances where home-cooks or small caterers post their menu to multiple WhatsApp groups of residential association to solicit orders, and also gauge preferences and feedback (this is mainly only WhatsApp). In India, the concept of "dabbas" is quite popular in cities.

These are anecdotal of course. I don't have stats 😅