I rarely bruise on my legs, yes. But I'm not so much concerned with bruising as I am with being able to take the kick and keep fighting. So in other words, I condition not to avoid bruising, but to toughen my legs.

As I'm sure you'll find out, when you start sparring you're gonna have bruises and fractures everywhere (shins, feet, ribs, nose, etc). What makes the difference is being able to push through that burst of pain and finish the round (or fight), which is where pre-conditioning is helpful.