That's not true. There are "glueless" patch kits out there, very prevalent, that are just stickers, and I have not found them to be effective. And there are "glue" kits that are not vulcanizing (the glue is the same I think as "contact cement"), but with a true "vulcanizing" patch kit, the vlucanizing liquid causes a chemical reaction with an ingredient in the surface of the tube, as well as the patch, such that the tube and patch "melt" (actual technical term: "vulcanize") together.