You realize that a lot of people play with particle effects turned off right?
These don't see rain, which is a disadvantage equal to the advantage of not falling for smoke bombs.
However, it's more about allowing trolls to loom junk noone needs for the giggles. When Fin spawns his Champion Donkey, Testi uses his Elder's Wooden Stick and the Knights who say Ni throw Masterwork Stones in bagge's face... These are good times. Smoke bombs +3 would be a nice bullet point in this list.
Edit: Not saying I'm gonna loom the Smoke bombs, but I am sure someone will. If noone else, Fuma will have them