I love detailing MY interior, because its clean and as simple as a vaccum and Meguiar’s #40 on dash/plastics/doors, etc. I don't eat anything in my car. Every now and then there is dog hair, it happens. But it comes up easy, thankfully.
As for my friends cars (I don't detail professionally, just as a hobby and love for it), well some make me wonder why they let it get that bad, why they eat in there car, wish girls didn't shed like dogs, etc. But, I luckily haven't had any interiors nearly as bad as some as of us have seen on this forum with the crud, chocolate, cigs, dog hair, cat hair, dragon slobber and so on