for us that may build one or two manifolds in our lifetime to have something different and dont weld aluminum, its much cheaper to use steel, plus it lets me play at home with different ideas and fitments etc. sure if i was to go into manufacturing professional intake i would also make them aluminum, but they are not easier to make than an actual steel intake. lighter is also debatable because you have to use thicker aluminum. sure can they be lighter, of course, will they always be? no. again, can you make them out of steel yes. why would you? because you can and can't afford $4000 for a custom hogan or wilson intake.