Then a light went on over my head. Why not just cut down some
of my too-many bamboo stalks and use them?

We've done some of that, but we found that something was boring little
holes in the bamboo (and making sawdust).

I've read that the commercial bamboo is (a) very dry, and/or (b)
treated with something.

I like the bamboo stakes, and we have a few that we kept for the
garden, but especially for right near/inside the house, we didn't want
to risk attracting critters which might cause more trouble if they
started munching something besides the bamboo.