I am not one of them but quite a few programmers prefer not having to use the mouse at all when working.

The terminal is an old but astonishingly powerful user interface that is still evolving.

Good terminals can be very snappy and configurable in ways that most GUI are not.

There is also arguably an aesthetic/fetishism appeal to it.

I've worked in the terminal at some point of my career, as there was not many other choices, and I understand how someone can get really used to it.