Answering the Question
Is there any objective study on the effectiveness of drivetrain cleaning?
The short answer is that I have not seen or done any objective studies specifically addressing the pros and cons of cleaning a bicycle drivetrain.
All of the bicycle chain studies I have seen involved clean chains. There are two examples linked at the bottom of this answer.
My thesis is that there are no studies of this type is because they are very difficult to set up, very controversial (questionable parameters), and it would be difficult to turn the results into something people could use in the real world.
Sheldon Brown "Chain Maintenance"
Chain maintenance is one of the most controversial aspects of bicycle mechanics. Chain durability is affected by riding style, gear choice, whether the bicycle is ridden in rain or snow, type of soil in the local terrain, type of lubricant, lubrication techniques, and the sizes and condition of the bicycle's sprockets. Because there are so many variables, it has not been possible to do controlled experiments under real-world conditions. As a result, everybody's advice about chain maintenance is based on anecdotal "evidence" and experience. Experts disagree on this subject, sometimes bitterly. This is sometimes considered a "religious" matter in the bicycle community, and much vituperative invective has been uttered in this regard between different schismatic cults.
The Rest of the Question
From the original post:
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?
Your criteria for success are:
- Drivetrain is quiet
- Shifting is impeccable
- Duration 2000 miles
In your experience you didn't clean your chain and it was still quiet and shifted well - so why bother cleaning a chain at all? It's a reasonable question.
Here are some reasons people might bother:
- Cleanliness, this person would say "I want a clean chain above all other considerations"
- Performance, "I want my bike to perform at it's best." Friction would be one aspect of performance.
- Appearance, "I want my bike to look good at all times"
- Durability, "I want my drivetrain to last as long as possible no matter what"
- I like working on my bike""
Usually people are looking for a "sweet spot" between two critera. For example, effort vs. improvement in durability. Others may have a complex set of criteria that change over time. The search for a sweet spot based on personal criteria is the reason an objective answer is so difficult to arrive at (as Sheldon points out).
Here are some studies that focus on reducing friction in the drivetrain.
"Chain Efficiency Testing" looks at how chain wear affects friction.
"Chain Lube Efficiency Tests" focuses on which chain lube reduced friction the most.