Linux is in general still fairly secure when it comes to threads from Virus or Malware, especially those running Distros with the SELinux module enabled. (For a moment, lets forget it’s co-designed by NSA).
You still hear a lot of people running Antivirus software on their Linux, and might wonder why they waste capacity and responsetime on that.
Don’t help spread Malware to other systems
The major reason is to make sure you dont help spread Malware to other systems. You might send me a file, or I might download an infected file that dont affect my system. But I can easily forward the file to you, and thereby infect your system without wanting to if I dont know its infected. And the only way to spot if its infected, is to run a Antivirus program.
I user the free suite called ClamAV, that that havent caused any problems on my servers or workstations.