To clean or not to clean...

When a record hits my door...new, used, borrowed, stollen it gets cleaned and a new set of clothes....!

According to the real experts, there is no question! ALL vinyl records should be cleaned, even new ones. New records will have the residue of mold release compounds (old ones may, as well, if they've never been properly cleaned before) that should be removed, along with any other microscopic and non-microscopic detritus that may be present after pressing. There are many methods of doing this effectively. Of course, proper care, handling and storage of records are very important, as well (e.g. quality anti-static sleeves). After cleaning, you might want to consider using a product called "LAST" record preservative. Google the LAST Factory and see what you think. However, don't take my word for it. Read this:

Precision Aqueous Cleaning of Vinyl Records-2nd Edition - The Vinyl Press

Not an easy read but as informative a source on this subject as you will ever come across.  You might also want to read what the Library of Congress has to say on this, as well.

To clean or not clean a new LP depends on how much you value your cartridge and stylus, and how much you value getting the best sonics off the record.
It hurts nothing to clean prior to play so I do some form of it whether it’s a light brush or an ultrasonic clean. Proper care and your records will last a lifetime and continue to sound their best.
Also recommend cleaning the stylus periodically and replacing paper record sleeves.

I just play new LP's, and I only buy used if Very Good +, and look at them: looks clean to me, typically successfully play them.

My cleaning is for my old dirty records, ones others gave me, and if I take a chance in a used store on something I think needs and will clean well enough.

Training your brain to ignore infrequent random noise was/is part of the Vinyl experience. I had it, lost it during the many years of CD only, had to regain it. Recurring noise from scratches are regrettable, I don't buy or sell scratches.

Depends on how much you like paying for a cartridge rebuild.

Someone did an analysis of record groove gunk: he reported that it’s a third grease, and third fluff, and a third diamond dust (presumably from a stylus). That’s a grinding compound, ready and able to reshape your stylus.

No record touches my Koetsu until it’s been cleaned ultrasonically. According to a photomicrograph at 1000 hours, the stylus shows minimal wear. Even the authorized dealer advised against a rebuild.

So follow MC’s advice if you like to burn money and destroy precision instruments. I don’t.