It wasn't specified in your previous post but if you are actually talking about people hitting on hard 17+ with only 2 cards, they are certainly not highly experienced players you're right. It seems to be better to hit on a hard 17 when the dealer has 9+ and you are one card away from the Charlie, but not more than that.
However sometimes, for some reason people are convinced the dealer has a bigger hand than themselves and they just try their luck even if odds are bad.
Anyway the X card Charlie rule encourages people to hit on the whole, you have to keep that in mind when you play at a table applying this rule, that's what I meant.
Honestly, I have seen people hit with 20 on their hands, so I am not entirely sure if that's a good idea to judge people because they could do anything. Like they could have stayed and still won 99% of the time, but they still hit because they wanted blackjack or something I suppose, or a more guaranteed thing, this isn't their style, they just do it for that hand.
In the end, we should not really try to find out what people are doing and why they are doing it, they play blackjack, infinite one, or whatever version in a way that it may not sense to us, it's just the way people gamble. 15 is the hardest for me for example, there is a good chance I could lose if I hit, or lose if I stay, but that's just me, people may have different results.