But, you know they are here.

They can be turned off.

They require an internet connection.

They are not meant for tracking, and intent is important.

They provide other features than tracking.

They are expensive, and battery don't last. People won't use them to track their ex wife for months.

It's like comparing a gun and a knife. Sure, you can kill with a knife, but it's harder, and initially the knife is made for cutting carrots.