Making money (cryptomining, CCN theft)?
Stealing data (SSNs, other identity documents)?
Ransoming the data for money?
In the end of the day, most cybercrime is focused on making money, so wiping a system has zero utility (especially as it would tip off the owners to your presence).
It's acknowledged that some high-profile ransomware attacks had the ulterior motive of wiping data. They used the ransomware as a front and really just wanted to do damage, not make money.
Not all viruses do it intentionally, some are originally rather harmless but has unfortunate side-effects in its replication code. For example, when you use a floppy disk in a different format, the virus tries to overwrite it anyway...