Product Placement in Mass Media

I have recently started watching the Big Bang Theory and it struck me that every other scene has a real product, but I have never thought about shameless advertisers sticking random products into this show because the advertisements plug in perfectly with the show because it adds a sense of realism. I mean when they say in one episode " Now I have to make a stop at Walgreens to buy more eyeliner" I felt like I knew where they were going cause I live next to a Walgreens and I can picture where the characters are going and what they are doing. Maybe I'm just reading too much into this but let me know what you think in the comments section whether or not you agree with me.