If the user follows a link to an article or video, there's a high chance it'll be the end of their reddit session, due to distraction or back button capture. There's also a high chance the browser will unload the reddit page causing a flash of no content and potentially losing the user's scroll position. After a few rounds of this the user will leave in frustration.

Now they could use the tabs feature, but this is again a lost opportunity to have them browse some comments etc. Plus, if they need to browse for another purpose, you'll just be one or ten of a hundred open tabs instead of one of the couple of recent apps.