Adding to the accepted answer, wiping definitely prevents the operation of "unformatting" programs (or the FBI) who can recreate some or all of what was on the disk before formatting.
Wiping takes a lot of time. But I do know of some geek-fanatics who wipe their free space periodically, as a matter of course. Disks are not going to wear out from this any more than they would from defragmenting, but I would not make either one a daily practice.
As for full-disk wiping, I wouldn't bother unless I was selling my computer and just didn't want fragments of my email all over the disk.
Your question mentions ransomware. If my computer were to be hit with Ransomware I would just laugh and do a full-system restore. It would start by recreating the partitions (including formatting) and rewriting my files as they were before the problem hit. I use Acronis TrueImage for this, and have tested restores many times so I have full confidence that it works fine.
Anything else left over from before would still be on the disk, but wouldn't be considered anything but free space after the restore, so it can't hurt anything.
Especially if ransomware has encrypted it. In that case you can consider their encryption the equivalent of wiping with random numbers.