Well, the selection of wood would be the first problem. I have tried a large number of them, and not all wood works. You need something that resists denting so training with it won't wear it out in a month; that has the right density so it won't be too light or too heavy; that resists breaking; that has the right surface texture so if you need to slide your hand over it, you can do it efficiently; that is strong, even, smooth, straight-grained, tightly-grained in the length you want; that has been properly treated (air-drying and kiln drying changes the wood differently); and so on.

Not all wood, even of the same "type," is equal. Hickory is good for making tool handles, but only some varieties of hickory, apparently. So, great, let's find the right variety, processed the right way, and make a stick out of hickory, right? Well, guess what, hickory dents easily (relatively speaking). I have some sticks made out of Brazilian ironwood. It's wonderful in every way except that it looks too pretty to use. It's also rather dense, and I feel slowed down by it. I have tried a lot of different woods, and some surprised me, but most disappointed.

You can also use engineered wood, and for a while I thought it was the prefect wood except for the density. But then I saw a beautiful piece shatter into pieces suddenly. No, thanks, I don't want to end up holding a stump in a fight.

And then the tools you make apparently make a difference. I personally use machine-made sticks that certainly went through sanding, but some woodworkers claim that sticks cut with a very sharp blade, unsanded, are more resilient.

We haven't even talked about rattan vs. wood...