This is analogous to Facebook moving from individual walls to a newsfeed. Why did they move to newsfeed? Easily consumable ad units.

People WILL get used to it, and advertisers will soon have programmatic access to ads that will show in the Discover section. Whether or not they will add value to the advertisers with this format is the real question.

This change is no surprise to me, nor will they change it. Driven by the need for ad revenue [0]

[0] - https://news.ycombinator.com/item?id=14983800#14985153