a question for Shiva

So the other night, Sonny boy was reading an ACK. I forget which one, but it was one with Lord Shiva in it.
He'd just been to the Bannerghatta National Park where they'd seen a snake swallow another one whole and was still a little dazed by that..
And so Sonny boy was looking with new eyes at the serpent coiled around Lord Shiva's neck.

Amma,look at this snake around Shiva's neck!
*Immersed in Ramesh Menon's Mahabharat* mmmm, Sonny boy....

Amma, is that a COBRA!??
Yes, Sonny boy.

Why is Shiva wearing a snake like that around his neck, Amma? Isn't it dangerous?
The snake won't do anything to Shiva, Sonny boy. Its His pet.

Pet?? Like Trinity?
Yes. *by now distracted from the Mahabharat*

A pregnant pause and then- Amma, but why does Shiva have it on his neck?? Why can't the snake crawl after him everywhere? Like how Trinity walks after you?



I was stumped.
And I was reminded of this question of his long back.....