The point is to assure the strongest possible bond between the tube and the wood/plastic blank.
Wiping with acetone (or some other solvent) is intended to remove any grease left on the tube from its manufacturing process.
Many folks scuff the tube with an abrasive to provide a mildly rough surface for the glue to adhere better. The thinking is that the glue may not form a good chemical bond with the metal tube, but it will cure in the gap between the wood and the tube, and if the tube has been scratched, the glue will cure in those scratches to lock the tube into the blank mechanically.