IMO a large part of the reason is Escapees doesn't promote this board with the anywhere near same enthusiasm they have for their Facebook groups, including one for new RVers. All of their Facebook groups get daily updates and promotions. They don't do the same for this Forum. It's rarely mentioned at all and never mentioned on Facebook.
The reason is probably the numbers - Escapees Facebook group has 9100 members. Xscapers has 16,000 members and the newcomers group RV to Freedom has 41,000 members. Every time Escapees posts an update it's seen by all the people who've joined that group the next time they sign into Facebook.