Sometimes, a handcuff may be obvious but expensive to grab during a draft process.

Then there are situations like with the 49ers. Elijah Mitchell was an obvious, high-value handcuff. Shanahan loves him. Unfortunately, his injury rate is on the extreme side, but he was still an obvious pick for a CMC owner until he got hurt.
With Mitchell gone, the backup is Jordan Mason. Unlike Mitchell, he came cheap in drafts. In the league where I go against CMC tonight, I drafted Jordan with the 150th pick and he probably would have been available even later if I'd let him slide.

Here's a key to fantasy football:
Have the hottest waiver wire guy of the week on your roster the week before he's the hottest waiver wire guy.

we can't expect Mason to be Mitchell, but he was so inexpensive that it was a bit of a no-brainer to have him instead of a second QB, especially with the concerns about McCaffrey's health.