I am just adding my voice as well. I find it unethical of Hubspot to not solve this problem because this seems like they want to artificially increase the contact databases size and consequently the cost for the client to maintain it. Moreover, we heavily rely on the system to help us remain GDPR compliant and reduce the effort to do so through automation. If our sales executives have to spend 60% of their time cleaning up data our company will suffer the consequences.
Hubspot, fix this problem - this is not rocket science and you are creating risks and unnecessary costs for your clients! All you need to do is differentiate between TO and CC contacts (Drill-down-source 2) for workflow and list filtering, and integrate a simple switch on the plug-ins to exclude CC contacts from being logged. This should take no less than a day or two to develop!