There were plenty of destructive viruses. Some (e.g. CIH) would erase the MBR of the disk making it unbootable. Others like ILOVEYOU would overwrite user's data directly. Blaster specifically had a message about Windows' poor security and tried to DDoS Windows Update.
Sometimes viruses are written to by self-limiting. MyDoom, which caused about 10% of all email traffic for a time, was programmed to deactivate on a certain date. Also once viruses get to a certain level of infamy they get a lot of attention. Blaster was mitigated in just days, so by the time it started its DDoS it was already mostly wiped out.
Sometimes viruses are written to by self-limiting. MyDoom, which caused about 10% of all email traffic for a time, was programmed to deactivate on a certain date. Also once viruses get to a certain level of infamy they get a lot of attention. Blaster was mitigated in just days, so by the time it started its DDoS it was already mostly wiped out.