Exactly. A TUI is not a replacement for a GUI where human interaction is essential to the process.

But, very few computer processes require direct human input. The overwhelming majority of individual operations are performed silently in the background. The presence of a TUI in an image modification program allows for certain operations to be performed automatically, in the background, without a human ever needing to be involved. I actually needed to do this, to add what was basically a watermark and a date stamp to a PDF document via an image modification program. Repeated 80-120 times a day, 6 days a week. A TUI allows for the tying together of a half dozen simple operations into a functional system.