newbroom, most of the best ones have tubing, some have tubing at the transition where the stummel and shank come together and the stem also has a piece of tubing for the fit to the bamboo, none have complete tubing going through like a Dunhill innertube would.
There are other types of tubing used today other than the original stainless tubing originally used, there is aircraft grade aluminum tubing and carbon fiber tubing which is inert and can be stronger than its metal counterpart and lighter.
I always thought, and this is mere conjecture on my part, that the original use of bamboo came about because a maker had a stummel that was too nice to discard and perhaps a problem area was found on the original shank so the stummel was fitted with a bamboo shank saving what may have ordinarily would have been discarded. Today I'm sure most of the pipes with bamboo were destined to be made with that medium, whatever the case I think it's a splendid look. Cheers.
banjo