It is difficult for me to imagine any workplace would not have a qualified employee train the new person before leaving.
Well, there are two occasions when this happens.
A. Retirement - the time frame for planning on a replacement is too long - so management forgets about it 'til it's too late.
B. Employee quits (gives two weeks notice) - and two weeks is rarely time enough to hire a replacement (even if the replaceement is an in-house transfer, you usually have to "advertize the positon" and do interviews and evaluations).
Also, today's workplace seems adverse to succession planning - no matter how often they get burned.
It's even more fun when a worker is a "one man show" - Woody is the only billing clerk at his market; there are no comprehensive written procedures for the job; if he should be absent for more than a day, they would be required to call in someone from out-of-town and hope they could help (of course all of the out-of-town candidates are in "one man show" jobs of their own. The store has no provision for Woody to ever be able to use his vaction time.
der Brucer