These dudes are quite useful. But even more useful in multiplayer. If you manage to get them inside a base they can unlock doors during raids. And they can throw poop! You can also equip them with hats which looks better on them than hoomans.
They are surprisingly good at Fighting Alpha Creatures due to their ability to fling poop and slow them down, I can easily solo an alpha raptor with an argentavis so long as this little monkey is on my shoulder