Why do national laboratory presentations contain so much info per slide? I've seen many, many examples of scientific presentations from the National Laboratories in which virtually every slide is oversaturated with information.  If this were an isolated event, I wouldn't have given it any thought.  But I've noticed this pattern in presentations over many years from among presenters hailing from US national laboratories.  Though my field is computational science, I've seen talks from national laboratory scientists in other fields and their presentations also have this same characteristic.

In academia, I've been taught to keep slides as simple as possible, with as little info per slide as necessary.  My understanding is a presentation should be though of as an "advertisement" for the paper to be published.  Thus, presentation slides should be designed to preserve the audience's interest.  One method of keeping the audience interest is to not overwhelm them with too much information all at once (e.g., not too much text and not too many pictures in a single slide).  I presume this is universally true, regardless of discipline.

However, the overwhelming majority of national laboratory presentations that I've seen seem to fill up virtually every available space with as much information as possible.  Why do presentations from national laboratories tend to contain so much information per slide?  How does this meet the needs of their target audience?
Let me try to answer for the tendency in my own discipline (particle physics) where we have this problem across the board (i.e. universities too). 

Much like questions and answers on a Stack Exchange site, those slides are expected to form a resource for future investigators. We know there is too much there for anyone to absorb in the meeting, but we also know that more people will dig these slides out of the archive over the next year and study them then actually attended the meeting in the first place.

Yes, in an ideal world there would be a technical report and a deck of slides, but in fact there are only the slides.



Personally I try pretty hard not to do this, and the result is a lot of backup slides and a lot of little URLs hanging around the bottom of the slides.



As an aside, I think that PowerPoint and similar polished slideware makes stuffing them (over-)full way too easy. I use a LaTeX base for mine (just the old slides class with my own library of macros for a long time, but I've started using Beamer) and these tools encourage a better style. 

Alas, I know all the tricks to squeeze on just one more thing.