Your vacuum manufacturer probably has a monopoly on vacuum bags for it's machine because it's niche enough for nobody else to care about making alternative bags

Your vacuum manufacturer probably has a monopoly on vacuum bags for it's machine because it's niche enough for nobody else to care about making alternative bags. If someone decided that they wanted to, they could. This isn't the case with the iPhone. It isn't niche and plenty of people want to build and be listed in alternatives, but they are prevented from doing so.