1. Humans hate inequality, esp. those who are on the losing end, but it seems to make everyone unhappier in general. Inequality is useful, but probably needs some managing.
2. Massive wealth generated in modern societies, though it tends to fall into the hands of a few (exponentially so), is generated by having a society/collective. If you have more wealth than you could ever generate with your own two hands, then you're benefitting from society in a major way, regardless of how much society takes back. (Even this is not strictly true--what you can generate with your own two hands depends on education, inventions society has given to you (like language), etc. It's hard to calculate one's debt to society.)