There are people who say they did it unintentionally, but I doubt that, because how could something they know be unintentional. I can only say they are just lazy to read the TOS of a casino which ends up harming themselves.
Rules are rules and you cannot claim to be innocent if you say that you unintentionally violate the terms and service. VPN usage is one common thing that most gamblers violate, and they do not know that they are doing it wrong.
For example, one may accidentally connect to a VPN that connects to a country prohibited or banned by a particular gambling site. This may result in the ban of your account if the site has strong security measures in place that detect where you are logging in. This may seems a small mistake but if you have big money in your account and your account is declared suspicious, it can be a big problem for the gambler.
Yes, whatever the reason, it is still a violation, and what I emphasize here is that I am not sure that someone accidentally breaks the rules if they already know the rules that apply in a casino. Because they will definitely be careful.
And actually if it is not intentional, then we can also minimize it before they detect it. For example, someone uses a VPN and the casino does not immediately take action. And before the casino takes action, then we can contact them with what happened. But usually people will explain what happened after they have a problem.