Great UI comes from a strong leader who has specific tastes that everyone may not agree to. Execution of such a vision has to be highly controlled and it means

Great UI comes from a strong leader who has specific tastes that everyone may not agree to. Execution of such a vision has to be highly controlled and it means at times taking tough decisions and throwing away someone’s work. Open source is usually built with consensus and that is why it’s hard to follow “one vision”. Also hard to chuck out contributed code / features, specially when its voluntary since it’s not welcoming for new contributors.