You already mentioned it, gamblers lose control. Therefore, these gamblers will proceed no matter what, with or without that max bet option feature.
And besides, that feature can't be applied to all users as not all users do have the same behavior. So basically, that feature will be an option. And if a gambler came to the point that they want to continue their gambling activity on that particular session, they will just disable it and then that's it.
Again, that kind of behavior can just be addressed with the gambler's itself and not by websites putting lots of bankroll protection feature or something along those lines to their users.