At worst, you're somewhere unfortunate (doing something benign and unrelated) and someone brings you in for questioning about it. Wouldn't they do that in many cases even if your GPS was off (for example, from seeing you on cameras or other means)? It seems better to be able to bring in as many people as possible to get whatever information is needed to help with whatever situation was unfortunate in the first place.
If asked, it's not like you're going to lie and say you were somewhere else if your GPS was off. This way, you at least have proof you were exactly where you said you were.
Broadly speaking though, it is because the criminal justice system in the US focuses on conviction as the metric of success, not whether the conviction is of the correct person -- it is simply whether there is sufficient evidence to convince the jury, or sufficient fear to garner an quick plea bargain.
Tens of thousands of people confess to crimes is because they are given the option:
- 6 months for a plea bargain confession
- 10-20yrs if they "fight the charges" but get convicted in court
Many cannot afford expensive lawyers, so often times, the odds are stacked against them in court.
In more select scenarios, people confess to crimes they had nothing to do with because of pressure applied. One of many examples would be that of https://en.wikipedia.org/wiki/Jon_Burge
In summary: [Innocent person] + [cowprod electrocution] = [guilty confession]
While I would wager that I've dealt with police and the court system _significantly_ more than the average American, I will admit I haven't ever encountered ill intentioned law enforcement entities -- it's hard to believe I'm just lucky, though.
I think it's pretty safe to say bad LEOs make the news because they're extremely rare, and the backlash against each one found signifies that the oversight exists to ensure they don't last long.
