Clustering does not eliminate need for backups and logs
"Take databases as an example. In the dim, dark past, a database might be reliant on a technology like log-shipping to offer redundancy in case of an outage.
This relies on nightly backups plus up-to-date transaction log copies for the intervening period, and ultimately will result in some data loss (for any logs that had not completed transmission prior to the outage) and some service downtime while your DBAs work to bring the system back online.
Some people might refer to this as a warm standby. At best, it’s probably tepid.
With database clustering on the other hand, the storage between the primary and secondary nodes is shared – perhaps with a SAN volume or replicated disks – so there is no requirement for backups and logs to be shipped."
Database clustering does not eliminate the need for backups. Assuming you are talking about a geo cluster then it does eliminate the need for backups in a site failure scenario. There are other scenarios.
Take the example of the admin asked to anonymise a test database and who ran the SQL script against the prod database. All data effectively destroyed and the destruction synchronously replicated to the DR site by block level storage replication.
Without daily backups and 15 min log backups this would have been even nastier than it actually was (2 days loss of business).