Is it accurate to say that every program that responds to input has a main thread with an infinite loop?

I'm wondering if it's correct to say that every responsive program has at its heart a main thread like

while not quit
     if work to do
         do work

Example:

• HTTP listeners / web server
• User interface
• Service that executes jobs

Another way of phrasing my question:

Is it possible to create a program where no threads are executing until there is some type of stimuli (e.g. mouse click, network request)?