Rewards, social media and FB messenger

The Soylent rewards program gives you credit for purchases (kinda like cash back on a credit card)… They also give rewards for promoting Soylent on social media… I get that (even though like most aspect of social media, I have no interest in participating). But they also give rewards for contacting them on FB messenger… How does this benefit them?!? I don’t use FB messenger (it’s bad enough that Google reads my gmail… The price of a good spam filter I suppose). What’s the deal here? I thought messenger was a (mostly) point to point system? What would Soylent or Facebook gain from me connecting to Soylent via FB messenger?

Engagement is my guess