The only time I leave mine in is when I'm camping. When in storage, it sits just inside the main camper door. When camping, I need that space, and it won't fit easily thru any storage doors. I'm not leaving it on the ground, so it stays in. I don't really like to leave it there, but I don't have another good option.
As someone else implied, the less crumpled material, the more force is being transferred to your body, greatly increasing your chance of a whiplash-type injury. And just because your truck wasn't damaged, I am sure my Equal-I-zer spring-bar sockets would no longer be aligned very well. I've heard of many people getting new WDH heads after being rear-ended for that reason. And if it were illegal to leave the head in place, you can bet an insurance company would not pay for a new WDH head.
Not to mention, leaving the head in just looks stupid. The only thing worse are those idiots that hang a pair of flesh colored testes off of the receiver. So tacky.
Imagine some dude in a pickup with a front receiver and drawbar, rear-ending another pickup with rear receiver and drawbar. Hang on to your fillings!!
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
2004 Surveyor SV261T (UltraLite Bunkhouse Hybrid)
2006 Mercury Mountaineer V8 AWD Premier
Equal-i-zer WDH (10k), Prodigy Brake Controller