Having access to a restricted database user may well not grant access to all data, but being able to escape to the root system user could mean free access to th

Having access to a restricted database user may well not grant access to all data, but being able to escape to the root system user could mean free access to the data reading it directly off disk. Root access also provides many more opportunities for persistence. Most attackers don't want to be discovered, they want to remain and continue to exfiltrate. Exfiltration out-of-band will also be easier as root as you would be able to modify the firewall. Root may be a little less useful on a cloud VM where there is cloud level network isolation etc, but it's still a Bad Idea.