Straw poles are just too hard to climb . . .
Straw poll

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Poles can be climbed when made of wood, metal etc and placed firmly in the ground. Straw is very weak and brittle. It bends very easily and cannot hold much weight. Therefore, a straw pole (a pole made of straw) would be impossible to climb. Really not worth the effort when a joke has to be explained. (It's a play on words.)
https://www.strawpoll.me/19608454