Clarity and utility. This has to be the foundation of any User Interface.
I have worked with software companies providing designs for dashboards and network monitoring interfaces, taking what are often arbitrary concepts and communicating them in a clear, on-brand style. I've also worked on retail, kiosk UIs, document management systems for multiple blue chip clients and monitoring software interfaces in the defence sector.
While a UI primarily needs to fulfil an objective, 'find a document', 'buy a product', 'view a dashboard', sometimes they need to engage the user in a visual, creative way. This is where the right designer can add value.