I don't disagree with this, of course. Some startups do create some valuable services for people. But society would be better off if those services were owned by the people using them and the surplus value was going to more people rather than a few investors.
Ideally they would be one and the same, but the short answers is because more even distribution of money and power in a society is a good in itself (from my point of view). And because large amounts of wealth in the hands of small individuals is useless and even bad.
I have created and supported products I have no ability to use because I'm not a large enterprise, and I don't think I'm particularly unique. Because of that, I disagree that producers and users of a product would ideally be one in the same. If organizations are required to perform all development and support in-house, specialization will be difficult if not impossible, and innovation and improvement will slow significantly.
Wealth and power distributions are relative, and if you're saying that moving towards a more even distribution from where we are now would be a good thing, I agree. However, I don't think a perfectly even distribution is desirable or even possible.
Also, large amounts of wealth in the hands of a small number of individuals is far from useless (it's not buried underground or stored in a vault), and whether it's bad or not depends on the context.
