It's a freemium service that doesn't depend on ad revenue. Maybe they're not made of money as Facebook and Google are and that's the reason for not compensating.
This isn't some free service being run out of the goodness of somebodys heart. This is a company, that wants to make money. If a company has that many employees, they can afford a bug bounty program too.
1. What people are reading
2. What they will read
3. What they have read
4. What they are just bookmarking/RILing and not reading
5. Etc etc.
That's valuable data imho.
Maybe they're just being evil, you know, like Oracle.