That's pretty much what Robject said--old geezers--and, your point supports mine about the soft rule.
With the soft rule, there's not a lot of incentive to stop character generation. A player keeps rolling until he can't roll any more.
With the hard rule, a player could get a character that he really likes with the skills he wants and will voluntarily stop character generation for fear of losing the character by repeated attempts at Survival.
With the hard rule, as mentioned above by ffilz, you get a more spread out group of characters in the PC group rather than have them all old and about the same age.
you're vastly oversimplifying, and probably projecting YOUR reasons for the reasons to others as a blanket without actually understanding the range of reasons.
Pretty much every player I've had pushes for retirement with at least one character, usually most of their characters. The longer ones are strings of forced reenlistments, or are vilani characters. The longest non-vilani character was a sucky PC in SolSec, with lethal failed survival... and 13 terms due to forced reenlistment. I've only had a few who wanted to push to 7 terms, but they (and I) have done that, even in the face of failed survival = death.
Character death doesn't stop the retirement seeker player - only failed reenlistment or hitting term 5. Most of the 6 and 7 term characters I've seen over the years have been either vilani or involuntary. ALL of the 1 or 2 term PCs have been involuntary (forced out by failed reenlistment or failed survival).
Some select 3 terms, not because of failed survival rolls, but because of aging. Most, however, are forced. And it was the same with FailSurvival=death.
4 terms is a mixed bag - some chicken out due to a bad stat and aging, some are forced out before retirement, and some are simply satisfied with the skillset. (Or in a few, they were at the experience limit, and further terms would be balanced raising stats vs aging losses).
The only times I've seen intentional 0.5-2 term characters is when we've been rolling up NPCs.