> it's morally wrong to demand that people who build things should be expected to share the thing they build
They don't have to share them! If you want to invent something and keep it secret, by all means, be my guest! This only concerns people who specifically build things for others (i.e. already sharing them).
You're free to share or not, but if you decide to do so, the recipents are free to say whether or not you're being an asshole because of the way you're sharing. That's how I see market segmentation - douchy behaviour. It's purposefully creating waste and/or artificially limiting the value you give to customer in order to profit more.
See what cell phone manufacturers are doing: segmenting the market by launching dozens of different models at the same time (half of them barely usable, but that's a topic for another time), each with a different set of "features" - little less RAM, little more storage, sensor A and B included, sensor B and C included (note that a model with sensors A, B and C is usually missing).
A sane situation would be when they'd be launching a single phone packed with features - powerful CPU, lots of RAM, lots of storage. Or maybe two, second being the "economy version" or basically the previous year's top model. But launching dozens of models a time means a lot of unused cellphones floating around, a lot of incompatibile parts being produced, and a lot of people learning for the first time that you don't go cheap on a smartphone because companies are very happy to sell you crap that barely works at all.
They don't have to share them! If you want to invent something and keep it secret, by all means, be my guest! This only concerns people who specifically build things for others (i.e. already sharing them).