Anyone know the reason why so many mobsters seemingly drop their guns right at the scene after hits ?

I would have thought with finger prints, DNA etc that it would be a bad idea, especially in the time period when The Sopranos is set. I can understand back in The Godfather days when forensics was less capable.

But just watching the episode there, where Bobby drops his gun after the hit for the Canadian pill supplier people. Got me wondering again, why they do it ?