You seem to not understand that a "big supplier" of bike parts is still a small fish when it comes to industry in general. Metal printed parts are only so functional especially depending on what you have to test. If you want to just have a touchy feely part in your hand so you can see it plastic is the way to go. And even then depending on where you are there is likely someplace near you that will make you one off prototypes on a contract basis so you don't have to swallow the cost of your own printer.