Visible crew/equipment: In the Television Room, when Wonka is explaining how you will be home watching television, and a commercial pops up, and it wants you to try a Wonka bar (by reaching into the TV and getting it), you can see a cameraman standing behind the camera reflected in Wonka's glasses. It might be a little hard to see (try zooming in), but it's there. (01:27:40)
Visible crew/equipment: When Charlie is shining Willy's shoes near the end, you can see the reflection of a crewman in Willy's glasses when he glances to his right. (01:38:25)
Visible crew/equipment: Throughout the movie, whenever somebody has glasses on, it is quite easy to see the crew in the reflection of the glasses. This is most obvious in the television room but is visible in other scenes too.
Answer: Wonka is simply uncomfortable around people. Gum chewing is simply an annoyance he never had to put up with as a recluse.
JC Fernandez