The reason is maybe the least satisfying of all. Because there is a rule somewhere saying that all workstations have to have an antivirus, Linux or Windows, same rules. Since "apt install clamav" is easier than arguing against the rulemakers again, that's what we did. And it is also not completely stupid, Linux viruses exist, and detecting malware on unaffected system is good too, because chances are that uncaught files will end up on vulnerable systems later. But really, the main reason we installed an antivirus to comply with some corporate rules.
It's very important to distinguish between what is actually required for compliance, and what is being done in the name of compliance, and make sure that "compliance" isn't just abused to shut down discussions easily.
SOC2 does not have any criteria specifically requiring antivirus software.
The actual requirements are more generic; for example CC6.8: "controls to prevent or detect and act upon the introduction of unauthorized or malicious software". That doesn't even sound like an unreasonable requirement to me.
If your company reads "no computer without antivirus" into that, that's on your company (and what they put in their SOC2 Type 1). Of course AV manufacturers will gladly agree that it should be read that way, and auditors will be more familiar with that approach. But if you can achieve the same in a different way, that's ok too - you just have to write it down that way. And the auditors can be reasoned with - their focus is anyway more to verify that you can show evidence (e.g. screenshots) of actually doing what you wrote down.
The reason is maybe the least satisfying of all. Because there is a rule somewhere saying that all workstations have to have an antivirus, Linux or Windows, same rules. Since "apt install clamav" is easier than arguing against the rulemakers again, that's what we did. And it is also not completely stupid, Linux viruses exist, and detecting malware on unaffected system is good too, because chances are that uncaught files will end up on vulnerable systems later. But really, the main reason we installed an antivirus to comply with some corporate rules.