It all depends on the generics. I buy generic cereal. But only certain ones because other ones I have tried aren’t the same as the name brand and I like the name brand. Sometimes it’s as simple as texture difference or a difference in flavor.

In the case of my epi-pens, the generic injectors don’t work exactly the same and that can be a bit much in an emergency where your throat is swelling shut or you’re having difficulty breathing.

In the case of something over the counter, I’d still wager things like mouth feel, smell, or other sensory factors are a reason. Like for instance, I prefer the smooth coating on Advil to the matte coating on Motrin or other ibuprofen generic meds.