I think a lot depends on what continent you are talking about.
When I walk a Camino, I fly from the US direct to Spain without a transfer in London or some other city that might have a different policy. So I can only comment on what I have experienced in Spain and in the US, but I have never been told that the poles could not go on the plane.
When I go on the Camino, or when I go hiking in the US, I take the poles apart and put them in a small duffel bag. I use the duffel so that I can check them if I have a problem with security. The bag is empty except for my neck pillow for the flight and the poles. I also carry on my backpack. I have never had trouble getting them through the security machines in the airports of Chicago, Dallas, San Francisco, Seattle, Miami, DC, Madrid, and others I can't remember.
I have a huge preference for carrying everything on, and you will too if some of your checked luggage doesn't make it to Madrid and you have a few hours to get to the train station to travel to Sevilla. I know the odds are small, but it happens. And when it does, it is a huge pain. Buen camino, Laurie