I am very lazy when it come to my microwave.  If the package calls for 1:40, I'll enter 99 to save one button press and not have to move my finger to three different buttons.  
Package:  [1], move finger, [4], move finger, 
I'm lazy: [9], [9], move finger, [start]
In this example there is the added benefit of having the nine button close to the start button, but the compromise of one less second of cook time.  
If a package calls for wrapping, flipping, bending the box, or changing the power setting I won't purchase it (again).  

Edit:  I typed the following  
I'm lazy: [9], [9], move finger, [start]
Why did the forum change it to a circle then repeat the line without a circle?