Good point, most people however don't expect their phone calls to be private for this very reason.
> does the French government have a bad track record of abusing the capability of eavesdropping any phone communication?
I'd rather look into possible future scenarios, I don't know about past cases, but I don't really follow french politics. I know discussing politics is HN is not encouraged, so I'd just rather suggest to look up what's coming for France (and EU) if the current government fails and major powers switch. Sorry if you already know this.
> has this capability been useful for law enforcement?
In Hungary, Pegasus was used to eavesdrop on many citizens who were simply in an opposing position. Law enforcement is a good cover for data collection and of course can be effective, but we need transparency and safety to see if these tools are abused or not. There are no good answers I'm afraid.