Some people report that their chain checker has measured a new chain as significantly worn. I don't doubt their experience but mine is different. The simple Park checker is metal and isn't going to wear from use. After all these years, if mine measured a new chain as worn, I would suspect the chain. Lots more chance for variation with all those little pieces. As mentioned above, chains are consumables and not prohibitively expensive. There are explanations on the internet about checkers measuring this but not that, etc, etc. These all "sound good to me" when read, but I don't think there is any consensus among those who actually are equipped to understand these things. Even Shimano offers a simple checker tool. TL;DR, It's like chain lube. Any method is better than none.
