Managers are status seeking people.

Part of the status is signaled by showing how many <<subordinates>> they have and giving orders to them.

Part of the status is signaled by beign able to be out of office whenever they want vs the worker bees that must be at the office 9-to-5 M-to-F.

Having to politely ask things on slack to a worker bee that is probably working lying on a couch with a smoothie in it´s hand is a manager vision of hell.

tl;dr: it´s not a lack of workers performance, but a wounded manager ego.

edit: I have never been downvoted as fast as in this case. It took less that a minute. Did I struck a nerve?