I bought a set recently which was definitely padding its piece counts. The interior structure of a solid shape was constructed out of dozens of small 1x2s and could easily have been a handful of much larger pieces with no downside. I didn't consider the "more pieces = more perceived value" logic until this comment.
For a while the complaint was that Lego was making too many big, specialized pieces, so I'm amused that the current complaint seems to be that they're using too many small generic ones.
I had a weird build recently with the Luxo Jr model. There are a couple of cavities in the model that are partially filled in with very small parts. These parts don't connect in a way that makes then structural. I'm still puzzled why these parts are there.
I always charitably assumed that they designed models to utilize surplus pieces for the internal structures, pieces that might be hard to use elsewhere.
They may do that (designers have a "part budget" they can spend in various ways) but the real reason for weird colors inside models is to make it easier to build; especially since many of the models consist entirely of various shades of grey and black.
Various piece size also makes it easier to see if you got the wrong piece.
