Why cant metal detectors have longer ranges like 100 meters or higher?

[leviterande]

Hi, everyone, I have a question. metal detectors basically work by inducing a current into a non ferro conductor, the back emf is captured by the receiving coil and thus you have a signal. What I am wondering is why is the metal detector only capable of detecting for a range of only a few feet? The metal detector is similar to any radio Tx/rx.

For example, if you have a strong magnetic pulse train from your detector, and there happens to be a a conductor somewhere around half a mile or just 100 meters etc.. out from you,. it is bound that there will be a current induced in that distant conductor which in turn of course creates a magnetic field which is also spreading out and should reach the detector receiver? Why are these common detectors limited by a few feet?

My guess: making an induced current in a distant conductor is easy. But, perhaps receiving the signal of the induced current from the distant conductor is very hard? because the signal is very low? but really in our modern era of electronics, all signals can be detected?
please enlighten me

thanks
best regards
levi karl