Maybe they have other established ways to advertise?
It may be word of mouth as my fave gunmaker here in Texas usually has a serious backlog and many good references from his customers (including me). Occasionally he will post pictures of a project.
The man that made two of my double rifles posted each new project as he completed them and was involved with gunmakers in multiple other countries. Unfortunately, he passed away a few years ago and the gunmaker traffic on that forum has dried up. IMHO, a big loss for the forum.
On another forum that I frequent, there are several long term smiths and makers that participate and have for years. IMHO, they make an authoritative contribution to the forum.
