If eyeballs were that important advertisers would be banging down their doors to place ads. Reddit's problem is that it's full of anonymous people that are hard to reach with targeted advertising.
It’s true that users are anonymous to others, but Reddit still has treasure trove of data on what likes, dislikes, political leaning and in some cases current emotional state/wellbeing of individual users.
Unless they are stating that they can’t process this data, they surely should have enough knowledge to do targeted ads.
Most likely scenario is that they have not invested enough on RnD and BD.
