I suggested it as well, but I'm split on it after thinking over possible consequences.
I believe one of the problems is that people can turn off particle effects removing the effect of it, while other has to suffer FPS lag when they're thrown. Also, turning off particle systems also affects the rain visuals, and making people having to remove that to avoid lagging doesn't seem like the way to go. A weight decrease would probably make more people carrying smoke bombs, and having people trolling with them around mass melee to make people lag seems a bad thing.
If it didn't create FPS lags for a lot of players it would be a no-brainer though.