Wrong question!
The correct one to ask is why are all those Catholics who attend Mass only twice a year not fearful of spending eternity in hell for failing to obey God's commandment? This query should be quickly followed up with two others: Why won't this issue be discussed with these infrequent Mass attendees and why will so few of them be reminded not to approach our Lord in the Holy Eucharist if they have not been fulfilling their obligation to actively participate in weekly Sunday Mass without first bathing themselves in the healing and forgiving waters of a sacramental confession?