Well for me, earphone jacks are for sending the signal to my car stereo so I don't have to mess with CDs. And I have to set the volume on full to get proper signal. Sure, there might be better options, but what I have works. I could set the volume ten times higher than the max and still not risk damaging my ears, because I control it on the car stereo side.
If you need to send the signal to something else it would be better to buy something with a line level output and connect it to an amplifier.