To be contrarian - Facebook is transferring its own user base to Instagram at a quarterly rate which is convenient to shadow Snapchat. The people I see there aren't much different than the ones on FB every month. FB is notifying me that, every single friend on FB is now on Instagram.
My likes on Instagram aren't shown to my followers - (I hope ) and that's the main difference which affects my behavior. Likes on instagram are cheap, like a casual double tap. On FB or LinkedIn they're expensive.
It really depends on where you live. Instagram and Facebook are still achieving substantial unabated growth in developing countries. In the US, usage for FB's main app has pulled back a little, though remains pretty high.
The major difference in developed countries is that the new post-millenial generation aren't seeing the same usage patterns.
My likes on Instagram aren't shown to my followers - (I hope ) and that's the main difference which affects my behavior. Likes on instagram are cheap, like a casual double tap. On FB or LinkedIn they're expensive.