"most of them are (if advertised heavily)" is quite a claim without data to back it up.

At least for the one I tested none of them sent additional traffic over my connection. That's just one data point and I only looked to ones with port forwarding but still far away from your claim.

There are a shitload of VPN tests out there and testing id your connection gets used by third parties for not traffic is even possible for a layperson.

Please stop fear mongering without remedies or specifics.