Many people barely start games, let alone finish them. Look at achievement stats for things that happen very early on in games. You'll find achievements that happen 1-2 hours in with only 60% earn rates. I don't think it's meaningful to look at completion rate without first normalizing with the "starting" rate.

One quick example from my steam library: Terraria

- Chop down your first tree. (You can do this immediately after you start playing): 86.5%

- Craft your first work bench. (Can be done immediately after cutting a tree): 56.8%

- Survive your character's first full night (24 minutes of playtime): 78.8%