It is not necessary to interfere with GPS in a wider area to mask your own position. The GPS signal is very low power (below the noise floor). It does not take much effort to block it. For this reason, the in car maskers (aka jammers) will block signals over a wide area unless they are precisely engineered to stay localized. There are a lot of poorly engineered maskers out there. I study these maskers and how they affect WAAS for the FAA.

I'm not condoning this as a technique to remain "private" ... I'm simply stating that I understand why people are buying jammers and I agree that some of them should be allowed to have their privacy.

I'm not so sure about others. If you're driving a truck for a shipping company, I suspect it's their right to know where their equipment is.

What I don't understand is how a trucking company that has their unit jammed doesn't eventually figure that out and fire the driver.

[EDIT] The only thing I can think of is that the GPS is always recording, but only examined in the event of an accident. The driver can claim the unit was defective and not his fault, so there's no proof he was driving 90 in a 60 zone.

It's possible that early units weren't very reliable. If drivers started using jammers before the reliability improved than the company may just expect a high rate of failure.

The other option is that insurance companies and regulators want the GPS trackers installed, but the companies don't care as long as the deliveries get made.

There are limits on how many hours a driver is allowed to work, for safety reasons.

I don't understand your logic. If it's your car just don't install a tracker device?

You increasingly don't get a choice.

Could you explain? Who's preventing you from not installing (or later disabling) anything on your own car?

Law enforcement use them by placing them on cars they are following unbeknownst to the suspect. A jammer is an effective countermeasure.

In the US, SCOTUS did at least rule that they need a warrant for that.

I can't think of anything that meets the hyperbolic claim, but I know some insurance companies have introduced driving monitors to assess how safe your driving is and adjust your premiums accordingly.

Yes, but those are opt ins as far as I know. That is, you agree to have said device installed so you can be eligible for a discount.

Agreeing to have such a device installed and then installing a jammer doesn't strike me as logical.

Surely there's a better way, like disconnecting the external aerial that feeds the GPS receiver?