It's the standard way of asking this type of question in English :) Asking "Do you know judges?" is possible but it sounds awkward and might be used in some slightly different contexts. Asking "Do you know any judges?" is just the standard way of asking if any of the people you know are judges.
The general rule is that "any" is used for questions and negatives ("Do we need any rice?" "No, we don't need any rice.") and "some" is used for positives ("We have some rice in the cupboard.")
"Do you know some judges?" is technically grammatically correct, but 'some' in English is more often used for uncountable quantities, such as water in the example "Would you like some water?". Because it is much easier to count the number of judges that someone might know, "Do you know any judges?" is more correct than "Do you know any judges?".