The internal backup remains useful and can often help solve a problem.
But those internal backups only hold information about the state of the database, including structure and metadata. They do not back up the document files. And they are on the same hard drive as is the database.
A good backup strategy should contemplate contingencies such as the possibility of a hard drive crash. Backups should also be done with reasonable frequency. I use Time Machine for those reasons.
I also use Scripts > Export > Backup Archive, which is included with DT Pro and DT Pro Office. This produces the smallest possible compressed and dated complete backup file. This covers contingencies such as theft or a house fire, that would result in loss of my computers and Time Machine backups. Periodically I copy current archives to DVD discs and store them at my bank. That’s consistent with my motto: Belt AND suspenders!