Ben Shneiderman wrote in 1997:
Direct manipulation depends on… rapid incremental reversible operations whose effect on the object of interest is immediately visible. This strategy can lead to user interfaces that are comprehensible, predictable and controllable. Direct manipulation interfaces are seen as more likely candidates to influence advanced user inter- faces than adaptive, autonomous, intelligent agents. User control and responsibility are highly desirable.
That’s worth reading carefully and thoughtfully.
[Shneiderman, B. Direct manipulation for comprehensible, predictable and controllable user interfaces. Proceedings of the 2nd international conference on Intelligent user interfaces, 1997.]
More specifically:
Agent promoters believe that the computer can automatically ascertain the users’ intentions or take action based on a vague statements of goals. This author is skeptical that user intentions are so easily determined or that vague statements are usually effective. However, if users can specify what they want with comprehensible actions selected from a visual display, then they can more often and more rapidly accomplish their goals while preserving their sense of control and accomplishment.
I completely agree with Shneiderman. I wonder if “agent promoters” today have progressed enough to offer solid counterarguments.