I learned from working in marketing is you have to let go of your biases and assumptions about user behavior. In the beginning I found myself constantly thinking "why would anyone in their right mind click on this ad", but we know people click on ads. Most of us in tech are very different from your typical internet user at large.

We have to assume that smart people are working at Reddit, that they have tested the living crap out of this model, and have found it to be optimal.