"(Columbus, OH) - Yesterday, a voting rights coalition asked the federal court to stop Ohio’s practice of removing properly registered voters from its voter registration list simply because they have not voted in recent elections. The plaintiffs, who initiated the lawsuit in early April, are composed of civic groups and a longtime Ohioan who was disenfranchised by this process."
Civic Groups Ask Courts to Stop Unlawful Voter Purging Practice | Demos
This quote and link are to a liberal group since I thought that might help get you to read it. That's who doesn't want registration rolls purged of dead voters and voters who have moved. In Ohio, the Democrats found one voter who hadn't bothered to vote in two years and got purged but instead of having him reregistered they marched hin in front of a friendly judge and got the purging of registration rolls stopped. Thereby, saving the registrations of the dead and moved voters to be used by party hacks and deadbeats.
Bottom line, dead voters are staying registered because the Democrats desperately want them to stay registered.