Why should one clean a chain? I do understand that this may sound like a troll question but please bear with me.

I've always been a maniac about drive train cleanliness until I got a 11 speed bike and realized I didn't want to spend the ca$$$h on the only reusable 11 speed chain link. Cleaning with the chain on the bike is too messy for my taste. Therefore I rode ~2k miles (new bike) with only periodic lubrication (using a good lubricant). Result? Nothing obviusly bad happened. Drive train is unsightly but quiet. Shifting is impeccable. Which made me wonder why should one clean a drive train at all: the process is cumbersome and a shiny drivetrain gets messy in no time with road only use under dry conditions. So why bother at all? Is there any objective study on the effectiveness of drivetrain cleaning?
A lot of people are now out of the habit of doing chain cleaning beyond wipe down level.

The reason to clean thoroughly is a marginal improvement in wear life and performance. But the key word is marginal. What you get for the effort is below the threshold of what many would consider worthwhile, especially riding recreationally.

Note that the expense level of your chain is a major factor here. It takes the same amount of time to clean a $13 basic 8-speed chain as it does an $60 Campy Record 11 chain, so clearly there's more economy in maximizing the service life of the latter.