This is just my opinion (as an amatuer coin collector), but I'm really against any form of cleaning. I think the big mistake however that grading companies make is that when a coin is cleaned, a lot of the time they don't even grade the coin, i.e., give it one of the designated grade levels along the 70-point curve (this is my experience, I could be wrong, as I have never personally submitted a coin in for grade).
It is in my small opinion that the vast majority of coins will at some point in their lifetime be cleaned. This automatically makes uncleaned coins signfiicantly rarer. Also, the patina that a lot of uncleaned coins have is not something that can develop and form over the course of a week, month, or even a year. Patina on an old coin takes YEARS, DECADES, or even more than a CENTURY to develop. When you examine an old old coin, pre-1850, that hasn't been cleaned, that means that the toning on it has been forming over all those years to its current state. Toning is probably one of the longer and slower reactions that we as people can appreciate, as it can take generations to form and we can to a certain extent appreciate how long that time is (not talking about stalagmites, which can form over millions of years and is a time frame we simply cannot comprehend). When a person cleans a coin, it's kind of sad. Decades and decades of the surface of that coin slowly reacting with its environment are completely erased. As toning is somewhat dependent on where the coin has been, we also lose the knowledge of where it was stored, what kind of environment it was in, etc. The colors, patterns, and characteristics that make that coin unique are gone within 2-3 minutes of scrubbing/wiping. For that coin to appear the same way as it did pre-cleaning, we won't be alive to see it. It's gonna take another 150 years to form.
That being said, I'll still spend money on cleaned coins