Task scheduler can not be disabled in Vista...

Does anyone know the rationale behind not allowing one to disable the
Task Scheduler service (from SERVICES.MSC, at least) in Vista/Longhorn?
In addition, how does “Task Scheduler Engine” (taskeng.exe) figure in to
this as well? Although I try to kill or disable everything I can in an
effort to simply the system for debugging purposes, I can live with this
running, but I’m curious, as it seems a strange decision, both because
only a few other services discourage being disabled this way, and those
would appear to much more fundamental to basic operating system
functionality (RPC, Group Policy, Plug and Play, and a few others), but
also because historically the AT command line interface to this service
has been pretty heavily exploited.