Because it's an input signal not output, hence the line in
Even if it was an output, which it isn't as others have noted, headphone out and line out are not the same thing and can't be used interchangeably. Sound will of course come out of the headphone jack, but might have rather nasty side effects too.
I get what people are saying, but we have no idea what’s on the other end of that quarter inch plug, and it could be nice headphones.
Why isn’t it plugged into the headphone jack?
Because it's an input signal not output, hence the line in
Even if it was an output, which it isn't as others have noted, headphone out and line out are not the same thing and can't be used interchangeably. Sound will of course come out of the headphone jack, but might have rather nasty side effects too.
I get what people are saying, but we have no idea what’s on the other end of that quarter inch plug, and it could be nice headphones.