We skip collision on alot of small irrelevant statics, for two reasons: 1 being its annoying in this engine to get stuck all the time (a grown, trained soldier doesnt get "stuck" on small boxes or wooden planks) also it saves performance to have it with no collision.
I want to have almost all small, detail statics without collision, like for example in Source Mods, it creates smooth gaming.. ofcourse when objects start reaching the size so player can prone and hide inside, collision is needed, but well, boxes, cans, buckets etc shouldnt have any.