They probably feel that the non-targeted ad revenue they would make from EU customers would not be worth the server costs, costs to comply with the law, and potential fine costs (risk).
Maybe or it could be that they don't have a data compliance officer, which is mandated by the GDPR.
Or it could be that they just don't know what the issues are and have no clue how to get compliant. IP addresses are protected data and make you a data controller if you have log files.