What Would Be the Reasoning Behind Leaving Class D Amps On?

It's quite simple. Class D amps when on, they're just standing by and using little to no power and could stay on and on and on endlessly 

it’s been said multiple times on the forums that it’s best to leave solid state / class d amps on all the time as it sounds better.   turn off / unplug solid state equipment if going out of town or bad weather is coming.

tube equipment gets turned off when not being used.

So yes, and I've researched the threads. But I haven't heard the basis for why Class D might sound better.  I get little to no heat, they aren't tubes, etc.  

What's the science behind why they sound better.  Just curious.  

You can leave a class D amp on 24/7, including lightning storms, and if it fails, you simply put down another $200 and buy another one. 

It seems like most if not all recently designed equipment have a main power switch on the back with a power switch on the front that puts the unit in stand-by mode.  I’m not a double E but have to believe there is a good reason for this.  I have a class D and it doesn’t have an on/off switch on the front so I leave on most of the time.  I do tend to turn everything off when leaving for a week or two.  I’ve not noticed a significant change in sound quality either way.  I just trust the designers.