Sitting everyone down for pictures is almost gloating; but when you remove the obligations, people's desires to be nice, helpful and curious kick in so they take a look and click like.
But yeah, I'm surprised that companies involved in travel aren't all over social media. My only guess is that it might be difficult to change the messaging from "travel is exciting" to "travel with Xyz travels pty ltd is exciting" because of the industry's commoditization.
To be honest, it's just that social media already does most of the job for them, for free (travelers post pictures on their own, nowadays even tagging the location or establishment), so why push it?
So why even show it to them in the first place?