#2 Fear of Info Exploitation
#3 Hassle
#4 Country Restrictions
Further details of each reasons can be read on the added link by OP.
I myself one of those who against KYC procedure for betting purpose in this bitcoin/crypto gambling industry. I have to say that 4 above reasons are enough to represent my situation but the main important reason why I choose to gamble with crypto is about its anonymity. In case all crypto gambling sites requires KYC in the future, I think I will stop gambling as there is no reason for me to continue as I gamble for fun only so I do not want to reveal my identity in online gambling.
I am already in legal age and I like crypto because of it's anonymity I want to gamble or earn as an anonymous.
And it is not new to us that there are some identity seller in the black market or in Deep web.
And it is just hassle to send out your I.D or personal info besides there are tons of gambling site that doesn't need KYC why would we bother doing it ?