The Bloomberg terminal is the perfect example of a lock-in effect reinforced by the powerful conservative tendancies of the financial ecosystem and its permanent need to fake complexity.
Simplifying the interface of the terminal would not be accepted by most users because, as ethnographic studies show, they take pride on manipulating Bloomberg’s current «complex» interface. The pain inflicted by blatant UI flaws such as black background color and yellow and orange text is strangely transformed into the rewarding experience of feeling and looking like a hard-core professional.
The Bloomberg Terminal interface looks terrible, but it allows traders and other users to pretend you need to be experienced and knowledgeable to use it.
Interesting read on people taking pride in being able to use complex user interfaces.