Users hate change
"We know what's best for the user" is assuming you are even designing for the user in the first place.The user is often not the customer, and design changes are ultimately here to serve the company, not the user:- How can we increase number of ads users will tolerate?  
- How do we increase the amount of content users share?
- How do we increase the number of likes/hearts they send?I wouldn't be surprised if the lionshare of user backlash comes from decisions that weren't meant to serve the user in the first place.