Was the animation use-case forseen or accidental? If they thought they were making a slide show / ad / page flipping tool, I can understand prioritizing longer durations.
Apparently, GIF didn't originally support animation. It was added in GIF89a (https://www.w3.org/Graphics/GIF/spec-gif89a.txt) with the GCE (Graphic Control Extension). Which adds the delay time field which is the issue.
> vii) Delay Time - If not 0, this field specifies the number of
hundredths (1/100) of a second to wait before continuing with the
processing of the Data Stream. The clock starts ticking immediately
after the graphic is rendered. This field may be used in
conjunction with the User Input Flag field.
Given the "announcement" GIF image BOB_89A.GIF was itself a slide show with about 10 seconds between frames, clearly GCE was done with at least slide shows in mind.
Incidentally, that same GIF uses the text extension, something basically no modern thing that can show GIFs supports anymore.
Well, I think a poor-man screen saver was a common enough use case for that. That said, you can (or, rather, could) control the images.
There's a flag in GIF89a that allows the viewer to skip ahead to the next frame on user input. No modern GIF viewer supports this anymore either. BOB_89A.GIF used this feature to let you skip ahead if you didn't want to just passively watch the slide show.
