Sometimes a system is so new to the user, or so complicated, that they don’t know where to start, especially in a system that algorithmically generates imagery or sound. Rather than learning how the system works, the user would like to just see it in action as quickly as possible.
Instead of prompting the user to enter inputs one by one, a single click on a “generate” button seeds random values into the system and produces output based on those variables. The user may then be given the option to edit the results.
While this is a very effective pattern for first use and feature discovery, there is no reason to limit it to just that use case. In many instances, generative systems can produce pleasantly surprising results from random prodding, and allowing the user to “spin the wheel” facilitates playful exploration and serendipitous discovery. This may be more rewarding than directed or goal-orientated use, in certain instances.
Obviously the nature of the algorithm itself will determine how good the results are when generated from random values rather than considered ones, but even if the algorithm itself is prone to wildly variant results when operated via all possible variables, a randomized inputs feature can be tweaked to work within a sensible subset of variables that produces a good range of output.