For example many EU banks refuse service to US citizens due to them still being tax liable in their own country and the banks not waiting to deal with that shit. Or they refuse service to Iranians, Russians or other nationalities in case of conflicts. That's the definition of a risky customer and they're legally allowed to bail on.
But working legally in your nations arms industry is not the definition of a risky customer because you're a legal citizen with rights in your own country, your arms company operates legally with all the checks and approvals of the government, and the banks should as well. Therefore there's no risks coming from the customer here to the local bank because neither you or the employer are doing anything in gray legal areas to be a risk.