High res pic I took six years ago: 
The card reads: Warmest greetings from the DuMont publishing house. Have fun reading it!
The cover reads: Help, my cat is broken! 200 cats going beyond their limits
High res pic I took six years ago:
The card reads: Warmest greetings from the DuMont publishing house. Have fun reading it!
The cover reads: Help, my cat is broken! 200 cats going beyond their limits
A Facebook/Instagram/Reddit post doesn’t directly financially benefit them. You can’t monetise a single puppy photo or even a ton of them… At best you get some sponsorship out of it but even that is rare.
A physical book (usually) requires fronting a considerable amount of money AND it directly financially benefits the writer and publisher. So they’re literally profiting off your property, directly.
Placing ads between and beside such content is pretty direct profit. Look at the cat, they get paid for showing you some cat food brand.