It's kinda unknown how many people use this software daily. But what I do know is, it's a active community and new content is being released every day by the community. From clothes, to assets, to scene's to even plugins. There is something for everyone to enjoy.
I would not focus on how many people use this software daily but more about how much content is being offered. The official discord is also more alive then the forums.
As for Steam, I don't know the whole story but I believe that VaM is removed due Steam policies. Something about royalty fee's and community paid content. Some community content is behind a paywall, for example on Patreon. Valve wanted to have a share from community paid content aswell, since the paid content is advertised within the software. But I could be wrong though.