In game advertisemants. Now before anyone lynches me, hear me out. Imagine billboards or radio ads. Now they would also have to be lore friendly. So it wouldn't be telling you to guy to
For example a radio ad, buy levi blue jeans at your local retailer! Pre-war glory that will survive anything you can!
Now whats the benefit to the player? More content. First you get the ads, which if done right are immersive. Then the devs can also add in extra weapons/armor. (Basically as a thank you.) Also, since they are only billboards/radio ads they are easily avoided or ignored.
Ok, I am done with my truly horrible idea.