Why are there so many types of mech hanger? I have just stripped the threads on my mech hanger and I'm in the process of buying a new one. There are so many different types, even for one manufacturer, I was wondering what the reason for this is?

I understand why different manufacturers might use different designs but why should one manufacturer have so many slightly different products that all do essentially the same thing?
Some designs are patented, therefore cannot be shared among different manufacturers.

Within the catalog of a single manufacturer I don't know, maybe a mix of keeping compatibility with previous models but also pushing people to "upgrade" and buy more expensive parts.