I probably have a skewed view based on what gets posted on the internet, but it seems like it's a lot of "I don't recall" from everyone.
Absolutely. Many depositions (and in significant cases, nearly all of them) are videotaped; then for trial, each side creates a "documentary" consisting of selected excerpts — think of it as being like a segment of a news show such as 60 Minutes. A string of "I don't know" or "I don't recall" answers, or even unduly-long pauses before answering, can seriously hurt a witness's credibility.
And if a witness testifies differently at trial than s/he did at the deposition, on cross-examination the opposing counsel will pounce and play back the relevant portion(s) of the video recording to impeach the witness's credibility that way as well.
Finally, depositions are very often used to "prove up" basic facts, as 'rayiner said in the GP.
The other part of asking basic questions is that the deponent's statement under oath that he started as CEO on such and such date is evidence that's directly usable. A print out from a web page with his basic bio can be evidence but it requires more hurdles. When you need that information for color down the line, it's helpful to have it in the deposition transcript.