All sorts of bad things happen when we disable the Task Scheduler service, is that bad?

A customer disabled the Task Scheduler service by applying group policy to set Task Scheduler’s startup mode to Off. When they did that, they found that a lot of stuff stopped working. For example, the Start menu would hang for several minutes. Search stopped working. “Any idea what tasks could be causing the issue?”

The customer liaison added “Obviously this is a bad idea, but I couldn’t find any official statement to that effect.”

Aha, the customer is looking for documentation that explicitly states that a bad idea is a bad idea, presumably because they want to shift the blame for their bad idea to Microsoft.

We responded that a bad idea is a bad idea, even if it’s not written down anywhere.

In the meantime, the customer liaison was able to find official documentation that confirmed that a bad idea is a bad idea!

Guidance on disabling system services on Windows Server 2016 with Desktop Experience lists a bunch of services and what Microsoft has to say about disabling that service.

Task Scheduler

Service description	Enables a user to configure and schedule automated tasks on this computer. The service also hosts multiple Windows system-critical tasks. If this service is stopped or disabled, these tasks will not be run at their scheduled times. If this service is disabled, any services that explicitly depend on it will fail to start.
Service name	Schedule
Installation	Always installed
StartType	Automatic
Recommendation	No guidance

Each service on the system is categorized as follows:

• Should Disable: A security-focused enterprise will most likely prefer to disable this service and forego its functionality (see additional details below).
• OK to Disable: This service provides functionality that is useful to some but not all enterprises, and security-focused enterprises that don’t use it can safely disable it.
• Do Not Disable: Disabling this service will impact essential functionality or prevent specific roles or features from functioning correctly. Therefore it should not be disabled.
• (No guidance): The impact of disabling these services has not been fully evaluated. Therefore, the default configuration of these services should not be changed.

(Emphasis mine.)