Craps, and to a lesser extent Blackjack, have some shared experiences between the players. In craps, many of the players will be betting the same, or at least very similar, way. Since there is only one dice roll for the entire table, there is a lot of shared excitement. With Blackjack, say the dealer is showing a 6, it's most likely that nobody on the table will bust, so if the dealer busts, everyone is excited. A slot machine, on the other hand, is an entirely solo experience.

I rarely play any floor games, but one time I was waiting for some friends to wake up and I wandered down to the casino to play some video poker. I ended up winning $1500 on a royal flush at a nickel machine. What am I supposed to do, start running around the casino in excitement? It was around 8:30 in the morning and the places was pretty quite. Had my friends been there, I'm sure we would have had some hi-fives or something like that, but if I'm just sitting there playing by myself, I'm not going to have any sort of substantial showcase of emotion.

I think you're correct in that a lot of people sit at the slot machines for hours, losing their paychecks in the process, and it's destructive for them. They may be looking miserable at the machines. The people playing craps who are in the process of losing their paychecks are equally as miserable, they're just showing different outward emotions. The addiction isn't any healthier because the person appears to be having fun.