There are alot of different chemicals on a Soda Can than on Aluminum Foil. Most obviously, the label...
From what i've seen Aluminum foil is basically harmless and if someone wants to smoke and thats the only option they have why not? I personally don't smoke out of foil i have many glass pieces but not everyone does.
This is kinda what I've been thinking. The melting point of aluminum is really pretty high and no conventional lighter is gonna get hot enough. If I recall my HS chemistry not even a Bunsen burner was hot enough to melt it...